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    SubjectRe: [PATCH Part1 v5 28/38] x86/compressed/64: enable SEV-SNP-validated CPUID in #VC handler
    On Fri, Aug 20, 2021 at 10:19:23AM -0500, Brijesh Singh wrote:
    > From: Michael Roth <michael.roth@amd.com>
    >
    > CPUID instructions generate a #VC exception for SEV-ES/SEV-SNP guests,
    > for which early handlers are currently set up to handle. In the case
    > of SEV-SNP, guests can use a special location in guest memory address
    > space that has been pre-populated with firmware-validated CPUID
    > information to look up the relevant CPUID values rather than
    > requesting them from hypervisor via a VMGEXIT.
    >
    > Determine the location of the CPUID memory address in advance of any
    > CPUID instructions/exceptions and, when available, use it to handle
    > the CPUID lookup.
    >
    > Signed-off-by: Michael Roth <michael.roth@amd.com>
    > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
    > ---
    > arch/x86/boot/compressed/efi.c | 1 +
    > arch/x86/boot/compressed/head_64.S | 1 +
    > arch/x86/boot/compressed/idt_64.c | 7 +-
    > arch/x86/boot/compressed/misc.h | 1 +
    > arch/x86/boot/compressed/sev.c | 3 +
    > arch/x86/include/asm/sev-common.h | 2 +
    > arch/x86/include/asm/sev.h | 3 +
    > arch/x86/kernel/sev-shared.c | 374 +++++++++++++++++++++++++++++
    > arch/x86/kernel/sev.c | 4 +
    > 9 files changed, 394 insertions(+), 2 deletions(-)

    Another huuge patch. I wonder if it can be split...

    > diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
    > index 16ff5cb9a1fb..a1529a230ea7 100644
    > --- a/arch/x86/boot/compressed/efi.c
    > +++ b/arch/x86/boot/compressed/efi.c
    > @@ -176,3 +176,4 @@ efi_get_conf_table(struct boot_params *boot_params,
    >
    > return 0;
    > }
    > +

    Applying: x86/compressed/64: Enable SEV-SNP-validated CPUID in #VC handler
    .git/rebase-apply/patch:21: new blank line at EOF.
    +
    warning: 1 line adds whitespace errors.

    That looks like a stray hunk which doesn't belong.

    > diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
    > index a2347ded77ea..1c1658693fc9 100644
    > --- a/arch/x86/boot/compressed/head_64.S
    > +++ b/arch/x86/boot/compressed/head_64.S
    > @@ -441,6 +441,7 @@ SYM_CODE_START(startup_64)
    > .Lon_kernel_cs:
    >
    > pushq %rsi
    > + movq %rsi, %rdi /* real mode address */
    > call load_stage1_idt
    > popq %rsi
    >
    > diff --git a/arch/x86/boot/compressed/idt_64.c b/arch/x86/boot/compressed/idt_64.c
    > index 9b93567d663a..1f6511a6625d 100644
    > --- a/arch/x86/boot/compressed/idt_64.c
    > +++ b/arch/x86/boot/compressed/idt_64.c
    > @@ -3,6 +3,7 @@
    > #include <asm/segment.h>
    > #include <asm/trapnr.h>
    > #include "misc.h"
    > +#include <asm/sev.h>

    asm/ namespaced headers should go together, before the private ones,
    i.e., above the misc.h line.

    > static void set_idt_entry(int vector, void (*handler)(void))
    > {
    > @@ -28,13 +29,15 @@ static void load_boot_idt(const struct desc_ptr *dtr)
    > }
    >
    > /* Setup IDT before kernel jumping to .Lrelocated */
    > -void load_stage1_idt(void)
    > +void load_stage1_idt(void *rmode)
    > {
    > boot_idt_desc.address = (unsigned long)boot_idt;
    >
    >
    > - if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT))
    > + if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
    > + sev_snp_cpuid_init(rmode);
    > set_idt_entry(X86_TRAP_VC, boot_stage1_vc);
    > + }
    >
    > load_boot_idt(&boot_idt_desc);
    > }
    > diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
    > index 16b092fd7aa1..cdd328aa42c2 100644
    > --- a/arch/x86/boot/compressed/misc.h
    > +++ b/arch/x86/boot/compressed/misc.h
    > @@ -190,6 +190,7 @@ int efi_get_conf_table(struct boot_params *boot_params,
    > unsigned long *conf_table_pa,
    > unsigned int *conf_table_len,
    > bool *is_efi_64);
    > +

    Another stray hunk.

    > #else
    > static inline int
    > efi_find_vendor_table(unsigned long conf_table_pa, unsigned int conf_table_len,
    > diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
    > index 6e8d97c280aa..910bf5cf010e 100644
    > --- a/arch/x86/boot/compressed/sev.c
    > +++ b/arch/x86/boot/compressed/sev.c
    > @@ -20,6 +20,9 @@
    > #include <asm/fpu/xcr.h>
    > #include <asm/ptrace.h>
    > #include <asm/svm.h>
    > +#include <asm/cpuid.h>
    > +#include <linux/efi.h>
    > +#include <linux/log2.h>

    What are those includes for?

    Polluting the decompressor namespace with kernel proper defines is a
    real pain to untangle as it is. What do you need those for and can you
    do it without them?

    > #include "error.h"
    >
    > diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
    > index 072540dfb129..5f134c172dbf 100644
    > --- a/arch/x86/include/asm/sev-common.h
    > +++ b/arch/x86/include/asm/sev-common.h
    > @@ -148,6 +148,8 @@ struct snp_psc_desc {
    > #define GHCB_TERM_PSC 1 /* Page State Change failure */
    > #define GHCB_TERM_PVALIDATE 2 /* Pvalidate failure */
    > #define GHCB_TERM_NOT_VMPL0 3 /* SNP guest is not running at VMPL-0 */
    > +#define GHCB_TERM_CPUID 4 /* CPUID-validation failure */
    > +#define GHCB_TERM_CPUID_HV 5 /* CPUID failure during hypervisor fallback */
    >
    > #define GHCB_RESP_CODE(v) ((v) & GHCB_MSR_INFO_MASK)
    >
    > diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
    > index 534fa1c4c881..c73931548346 100644
    > --- a/arch/x86/include/asm/sev.h
    > +++ b/arch/x86/include/asm/sev.h
    > @@ -11,6 +11,7 @@
    > #include <linux/types.h>
    > #include <asm/insn.h>
    > #include <asm/sev-common.h>
    > +#include <asm/bootparam.h>
    >
    > #define GHCB_PROTOCOL_MIN 1ULL
    > #define GHCB_PROTOCOL_MAX 2ULL
    > @@ -126,6 +127,7 @@ void __init snp_prep_memory(unsigned long paddr, unsigned int sz, enum psc_op op
    > void snp_set_memory_shared(unsigned long vaddr, unsigned int npages);
    > void snp_set_memory_private(unsigned long vaddr, unsigned int npages);
    > void snp_set_wakeup_secondary_cpu(void);
    > +void sev_snp_cpuid_init(struct boot_params *bp);
    > #else
    > static inline void sev_es_ist_enter(struct pt_regs *regs) { }
    > static inline void sev_es_ist_exit(void) { }
    > @@ -141,6 +143,7 @@ static inline void __init snp_prep_memory(unsigned long paddr, unsigned int sz,
    > static inline void snp_set_memory_shared(unsigned long vaddr, unsigned int npages) { }
    > static inline void snp_set_memory_private(unsigned long vaddr, unsigned int npages) { }
    > static inline void snp_set_wakeup_secondary_cpu(void) { }
    > +static inline void sev_snp_cpuid_init(struct boot_params *bp) { }
    > #endif
    >
    > #endif
    > diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
    > index ae4556925485..651980ddbd65 100644
    > --- a/arch/x86/kernel/sev-shared.c
    > +++ b/arch/x86/kernel/sev-shared.c
    > @@ -14,6 +14,25 @@
    > #define has_cpuflag(f) boot_cpu_has(f)
    > #endif
    >
    > +struct sev_snp_cpuid_fn {
    > + u32 eax_in;
    > + u32 ecx_in;
    > + u64 unused;
    > + u64 unused2;

    What are those for? Padding? Or are they spec-ed somewhere and left for
    future use?

    Seeing how the struct is __packed, they probably are part of a spec
    definition somewhere.

    Link pls.

    > + u32 eax;
    > + u32 ebx;
    > + u32 ecx;
    > + u32 edx;
    > + u64 reserved;

    Ditto.

    Please prefix all those unused/reserved members with "__".

    > +} __packed;
    > +
    > +struct sev_snp_cpuid_info {
    > + u32 count;
    > + u32 reserved1;
    > + u64 reserved2;

    Ditto.

    > + struct sev_snp_cpuid_fn fn[0];
    > +} __packed;
    > +
    > /*
    > * Since feature negotiation related variables are set early in the boot
    > * process they must reside in the .data section so as not to be zeroed
    > @@ -26,6 +45,15 @@ static u16 __ro_after_init ghcb_version;
    > /* Bitmap of SEV features supported by the hypervisor */
    > u64 __ro_after_init sev_hv_features = 0;
    >
    > +/*
    > + * These are also stored in .data section to avoid the need to re-parse
    > + * boot_params and re-determine CPUID memory range when .bss is cleared.
    > + */
    > +static int sev_snp_cpuid_enabled __section(".data");

    That will become part of prot_guest_has() or cc_platform_has() or
    whatever its name is going to be.

    > +static unsigned long sev_snp_cpuid_pa __section(".data");
    > +static unsigned long sev_snp_cpuid_sz __section(".data");
    > +static const struct sev_snp_cpuid_info *cpuid_info __section(".data");

    All those: __ro_after_init?

    Also, just like the ones above have a short comment explaining what they
    are, add such comments for those too pls and perhaps what they're used
    for.

    > +
    > static bool __init sev_es_check_cpu_features(void)
    > {
    > if (!has_cpuflag(X86_FEATURE_RDRAND)) {
    > @@ -236,6 +264,219 @@ static int sev_cpuid_hv(u32 func, u32 subfunc, u32 *eax, u32 *ebx,
    > return 0;
    > }
    >
    > +static bool sev_snp_cpuid_active(void)
    > +{
    > + return sev_snp_cpuid_enabled;
    > +}

    That too will become part of prot_guest_has() or cc_platform_has() or
    whatever its name is going to be.

    > +
    > +static int sev_snp_cpuid_xsave_size(u64 xfeatures_en, u32 base_size,
    > + u32 *xsave_size, bool compacted)

    Function name needs a verb. Please audit all your patches.

    > +{
    > + u64 xfeatures_found = 0;
    > + int i;
    > +
    > + *xsave_size = base_size;

    Set that xsave_size only...
    > +
    > + for (i = 0; i < cpuid_info->count; i++) {
    > + const struct sev_snp_cpuid_fn *fn = &cpuid_info->fn[i];
    > +
    > + if (!(fn->eax_in == 0xd && fn->ecx_in > 1 && fn->ecx_in < 64))
    > + continue;
    > + if (!(xfeatures_en & (1UL << fn->ecx_in)))
    > + continue;
    > + if (xfeatures_found & (1UL << fn->ecx_in))
    > + continue;
    > +
    > + xfeatures_found |= (1UL << fn->ecx_in);

    For all use BIT_ULL().

    > + if (compacted)
    > + *xsave_size += fn->eax;
    > + else
    > + *xsave_size = max(*xsave_size, fn->eax + fn->ebx);

    ... not here ...

    > + }
    > +
    > + /*
    > + * Either the guest set unsupported XCR0/XSS bits, or the corresponding
    > + * entries in the CPUID table were not present. This is not a valid
    > + * state to be in.
    > + */
    > + if (xfeatures_found != (xfeatures_en & ~3ULL))
    > + return -EINVAL;

    ... but here when you're not going to return an error because callers
    will see that value change temporarily which is not clean.

    Also, you need to set it once - not during each loop iteration.

    > +
    > + return 0;
    > +}
    > +
    > +static void sev_snp_cpuid_hv(u32 func, u32 subfunc, u32 *eax, u32 *ebx,
    > + u32 *ecx, u32 *edx)
    > +{
    > + /*
    > + * Currently MSR protocol is sufficient to handle fallback cases, but
    > + * should that change make sure we terminate rather than grabbing random

    Fix the "we"s please. Please audit all your patches.

    > + * values. Handling can be added in future to use GHCB-page protocol for
    > + * cases that occur late enough in boot that GHCB page is available

    End comment sentences with a fullstop. Please audit all your patches.

    > + */

    Also, put that comment over the function.

    > + if (cpuid_function_is_indexed(func) && subfunc != 0)

    In all your patches:

    s/ != 0//g

    > + sev_es_terminate(1, GHCB_TERM_CPUID_HV);
    > +
    > + if (sev_cpuid_hv(func, 0, eax, ebx, ecx, edx))
    > + sev_es_terminate(1, GHCB_TERM_CPUID_HV);
    > +}
    > +
    > +static bool sev_snp_cpuid_find(u32 func, u32 subfunc, u32 *eax, u32 *ebx,

    I guess

    find_validated_cpuid_func()

    or so to denote where it picks it out from.

    > + u32 *ecx, u32 *edx)
    > +{
    > + int i;
    > + bool found = false;

    The tip-tree preferred ordering of variable declarations at the
    beginning of a function is reverse fir tree order::

    struct long_struct_name *descriptive_name;
    unsigned long foo, bar;
    unsigned int tmp;
    int ret;

    The above is faster to parse than the reverse ordering::

    int ret;
    unsigned int tmp;
    unsigned long foo, bar;
    struct long_struct_name *descriptive_name;

    And even more so than random ordering::

    unsigned long foo, bar;
    int ret;
    struct long_struct_name *descriptive_name;
    unsigned int tmp;

    Audit all your patches pls.

    > +
    > + for (i = 0; i < cpuid_info->count; i++) {
    > + const struct sev_snp_cpuid_fn *fn = &cpuid_info->fn[i];
    > +
    > + if (fn->eax_in != func)
    > + continue;
    > +
    > + if (cpuid_function_is_indexed(func) && fn->ecx_in != subfunc)
    > + continue;
    > +
    > + *eax = fn->eax;
    > + *ebx = fn->ebx;
    > + *ecx = fn->ecx;
    > + *edx = fn->edx;
    > + found = true;
    > +
    > + break;

    That's just silly. Simply:

    return true;


    > + }
    > +
    > + return found;

    return false;

    here and the "found" variable can go.

    > +}
    > +
    > +static bool sev_snp_cpuid_in_range(u32 func)
    > +{
    > + int i;
    > + u32 std_range_min = 0;
    > + u32 std_range_max = 0;
    > + u32 hyp_range_min = 0x40000000;
    > + u32 hyp_range_max = 0;
    > + u32 ext_range_min = 0x80000000;
    > + u32 ext_range_max = 0;
    > +
    > + for (i = 0; i < cpuid_info->count; i++) {
    > + const struct sev_snp_cpuid_fn *fn = &cpuid_info->fn[i];
    > +
    > + if (fn->eax_in == std_range_min)
    > + std_range_max = fn->eax;
    > + else if (fn->eax_in == hyp_range_min)
    > + hyp_range_max = fn->eax;
    > + else if (fn->eax_in == ext_range_min)
    > + ext_range_max = fn->eax;
    > + }

    So this loop which determines those ranges will run each time
    sev_snp_cpuid_find() doesn't find @func among the validated CPUID leafs.

    Why don't you do that determination once at init...

    > +
    > + if ((func >= std_range_min && func <= std_range_max) ||
    > + (func >= hyp_range_min && func <= hyp_range_max) ||
    > + (func >= ext_range_min && func <= ext_range_max))

    ... so that this function becomes only this check?

    This is unnecessary work as it is.

    > + return true;
    > +
    > + return false;
    > +}
    > +
    > +/*
    > + * Returns -EOPNOTSUPP if feature not enabled. Any other return value should be
    > + * treated as fatal by caller since we cannot fall back to hypervisor to fetch
    > + * the values for security reasons (outside of the specific cases handled here)
    > + */
    > +static int sev_snp_cpuid(u32 func, u32 subfunc, u32 *eax, u32 *ebx, u32 *ecx,
    > + u32 *edx)
    > +{
    > + if (!sev_snp_cpuid_active())
    > + return -EOPNOTSUPP;
    > +
    > + if (!cpuid_info)
    > + return -EIO;
    > +
    > + if (!sev_snp_cpuid_find(func, subfunc, eax, ebx, ecx, edx)) {
    > + /*
    > + * Some hypervisors will avoid keeping track of CPUID entries
    > + * where all values are zero, since they can be handled the
    > + * same as out-of-range values (all-zero). In our case, we want
    > + * to be able to distinguish between out-of-range entries and
    > + * in-range zero entries, since the CPUID table entries are
    > + * only a template that may need to be augmented with
    > + * additional values for things like CPU-specific information.
    > + * So if it's not in the table, but is still in the valid
    > + * range, proceed with the fix-ups below. Otherwise, just return
    > + * zeros.
    > + */
    > + *eax = *ebx = *ecx = *edx = 0;
    > + if (!sev_snp_cpuid_in_range(func))
    > + goto out;

    That label is not needed.

    > + }

    All that from here on looks like it should go into a separate function
    called

    snp_cpuid_postprocess()

    where you can do a switch-case on func and have it nice, readable and
    extensible there, in case more functions get added.

    > + if (func == 0x1) {
    > + u32 ebx2, edx2;
    > +
    > + sev_snp_cpuid_hv(func, subfunc, NULL, &ebx2, NULL, &edx2);
    > + /* initial APIC ID */
    > + *ebx = (*ebx & 0x00FFFFFF) | (ebx2 & 0xFF000000);

    For all hex masks: use GENMASK_ULL.

    > + /* APIC enabled bit */
    > + *edx = (*edx & ~BIT_ULL(9)) | (edx2 & BIT_ULL(9));
    > +
    > + /* OSXSAVE enabled bit */
    > + if (native_read_cr4() & X86_CR4_OSXSAVE)
    > + *ecx |= BIT_ULL(27);
    > + } else if (func == 0x7) {
    > + /* OSPKE enabled bit */
    > + *ecx &= ~BIT_ULL(4);
    > + if (native_read_cr4() & X86_CR4_PKE)
    > + *ecx |= BIT_ULL(4);
    > + } else if (func == 0xB) {
    > + /* extended APIC ID */
    > + sev_snp_cpuid_hv(func, 0, NULL, NULL, NULL, edx);
    > + } else if (func == 0xd && (subfunc == 0x0 || subfunc == 0x1)) {
    > + bool compacted = false;
    > + u64 xcr0 = 1, xss = 0;
    > + u32 xsave_size;
    > +
    > + if (native_read_cr4() & X86_CR4_OSXSAVE)
    > + xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
    > + if (subfunc == 1) {
    > + /* boot/compressed doesn't set XSS so 0 is fine there */
    > +#ifndef __BOOT_COMPRESSED
    > + if (*eax & 0x8) /* XSAVES */
    > + if (boot_cpu_has(X86_FEATURE_XSAVES))

    cpu_feature_enabled()

    > + rdmsrl(MSR_IA32_XSS, xss);
    > +#endif
    > + /*
    > + * The PPR and APM aren't clear on what size should be
    > + * encoded in 0xD:0x1:EBX when compaction is not enabled
    > + * by either XSAVEC or XSAVES since SNP-capable hardware
    > + * has the entries fixed as 1. KVM sets it to 0 in this
    > + * case, but to avoid this becoming an issue it's safer
    > + * to simply treat this as unsupported or SNP guests.
    > + */
    > + if (!(*eax & 0xA)) /* (XSAVEC|XSAVES) */

    Please put side comments over the line they comment.

    > + return -EINVAL;
    > +
    > + compacted = true;
    > + }
    > +
    > + if (sev_snp_cpuid_xsave_size(xcr0 | xss, *ebx, &xsave_size,
    > + compacted))

    No need for that linebreak.

    > + return -EINVAL;
    > +
    > + *ebx = xsave_size;
    > + } else if (func == 0x8000001E) {
    > + u32 ebx2, ecx2;
    > +
    > + /* extended APIC ID */
    > + sev_snp_cpuid_hv(func, subfunc, eax, &ebx2, &ecx2, NULL);
    > + /* compute ID */
    > + *ebx = (*ebx & 0xFFFFFFF00) | (ebx2 & 0x000000FF);
    > + /* node ID */
    > + *ecx = (*ecx & 0xFFFFFFF00) | (ecx2 & 0x000000FF);
    > + }
    > +
    > +out:
    > + return 0;
    > +}
    > +
    > /*
    > * Boot VC Handler - This is the first VC handler during boot, there is no GHCB
    > * page yet, so it only supports the MSR based communication with the

    Is that comment...

    > @@ -244,15 +485,25 @@ static int sev_cpuid_hv(u32 func, u32 subfunc, u32 *eax, u32 *ebx,
    > void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
    > {
    > unsigned int fn = lower_bits(regs->ax, 32);
    > + unsigned int subfn = lower_bits(regs->cx, 32);
    > u32 eax, ebx, ecx, edx;
    > + int ret;
    >
    > /* Only CPUID is supported via MSR protocol */

    ... and that still valid?

    > if (exit_code != SVM_EXIT_CPUID)
    > goto fail;
    >
    > + ret = sev_snp_cpuid(fn, subfn, &eax, &ebx, &ecx, &edx);
    > + if (ret == 0)
    > + goto out;

    I think you mean here "goto cpuid_done;" or so.

    > +
    > + if (ret != -EOPNOTSUPP)
    > + goto fail;
    > +
    > if (sev_cpuid_hv(fn, 0, &eax, &ebx, &ecx, &edx))
    > goto fail;
    >
    > +out:
    > regs->ax = eax;
    > regs->bx = ebx;
    > regs->cx = ecx;
    > @@ -552,6 +803,19 @@ static enum es_result vc_handle_cpuid(struct ghcb *ghcb,
    > struct pt_regs *regs = ctxt->regs;
    > u32 cr4 = native_read_cr4();
    > enum es_result ret;
    > + u32 eax, ebx, ecx, edx;
    > + int cpuid_ret;
    > +
    > + cpuid_ret = sev_snp_cpuid(regs->ax, regs->cx, &eax, &ebx, &ecx, &edx);
    > + if (cpuid_ret == 0) {
    > + regs->ax = eax;
    > + regs->bx = ebx;
    > + regs->cx = ecx;
    > + regs->dx = edx;
    > + return ES_OK;
    > + }
    > + if (cpuid_ret != -EOPNOTSUPP)
    > + return ES_VMM_ERROR;

    I don't like this thing slapped inside the function. Pls put it in a separate

    vc_handle_cpuid_snp()

    which is called by vc_handle_cpuid() instead.

    >
    > ghcb_set_rax(ghcb, regs->ax);
    > ghcb_set_rcx(ghcb, regs->cx);
    > @@ -603,3 +867,113 @@ static enum es_result vc_handle_rdtsc(struct ghcb *ghcb,
    >
    > return ES_OK;
    > }
    > +
    > +#ifdef BOOT_COMPRESSED
    > +static struct setup_data *get_cc_setup_data(struct boot_params *bp)
    > +{
    > + struct setup_data *hdr = (struct setup_data *)bp->hdr.setup_data;
    > +
    > + while (hdr) {
    > + if (hdr->type == SETUP_CC_BLOB)
    > + return hdr;
    > + hdr = (struct setup_data *)hdr->next;
    > + }
    > +
    > + return NULL;
    > +}
    > +
    > +/*
    > + * For boot/compressed kernel:
    > + *
    > + * 1) Search for CC blob in the following order/precedence:
    > + * - via linux boot protocol / setup_data entry
    > + * - via EFI configuration table
    > + * 2) Return a pointer to the CC blob, NULL otherwise.
    > + */
    > +static struct cc_blob_sev_info *sev_snp_probe_cc_blob(struct boot_params *bp)

    snp_find_cc_blob() simply.

    > +{
    > + struct cc_blob_sev_info *cc_info = NULL;
    > + struct setup_data_cc {
    > + struct setup_data header;
    > + u32 cc_blob_address;
    > + } *sd;

    Define that struct above the function and call it "cc_setup_data" like
    the rest of the stuff which deals with that.
    > + unsigned long conf_table_pa;
    > + unsigned int conf_table_len;
    > + bool efi_64;
    > +
    > + /* Try to get CC blob via setup_data */
    > + sd = (struct setup_data_cc *)get_cc_setup_data(bp);
    > + if (sd) {
    > + cc_info = (struct cc_blob_sev_info *)(unsigned long)sd->cc_blob_address;
    > + goto out_verify;
    > + }
    > +
    > + /* CC blob isn't in setup_data, see if it's in the EFI config table */
    > + if (!efi_get_conf_table(bp, &conf_table_pa, &conf_table_len, &efi_64))
    > + (void)efi_find_vendor_table(conf_table_pa, conf_table_len,
    > + EFI_CC_BLOB_GUID, efi_64,
    > + (unsigned long *)&cc_info);

    Yah, check that retval pls with a proper ret variable. No need to cram
    it all together.

    > +
    > +out_verify:
    > + /* CC blob should be either valid or not present. Fail otherwise. */
    > + if (cc_info && cc_info->magic != CC_BLOB_SEV_HDR_MAGIC)
    > + sev_es_terminate(1, GHCB_SNP_UNSUPPORTED);
    > +
    > + return cc_info;
    > +}
    > +#else
    > +/*
    > + * Probing for CC blob for run-time kernel will be enabled in a subsequent
    > + * patch. For now we need to stub this out.
    > + */
    > +static struct cc_blob_sev_info *sev_snp_probe_cc_blob(struct boot_params *bp)
    > +{
    > + return NULL;
    > +}
    > +#endif
    > +
    > +/*
    > + * Initial set up of CPUID table when running identity-mapped.
    > + *
    > + * NOTE: Since SEV_SNP feature partly relies on CPUID checks that can't
    > + * happen until we access CPUID page, we skip the check and hope the
    > + * bootloader is providing sane values.

    So I don't like the sound of that even one bit. We shouldn't hope
    anything here...

    > Current code relies on all CPUID
    > + * page lookups originating from #VC handler, which at least provides
    > + * indication that SEV-ES is enabled. Subsequent init levels will check for
    > + * SEV_SNP feature once available to also take SEV MSR value into account.
    > + */
    > +void sev_snp_cpuid_init(struct boot_params *bp)

    snp_cpuid_init()

    In general, prefix all SNP-specific variables, structs, functions, etc
    with "snp_" simply.

    > +{
    > + struct cc_blob_sev_info *cc_info;
    > +
    > + if (!bp)
    > + sev_es_terminate(1, GHCB_TERM_CPUID);
    > +
    > + cc_info = sev_snp_probe_cc_blob(bp);
    > +

    ^ Superfluous newline.

    > + if (!cc_info)
    > + return;
    > +
    > + sev_snp_cpuid_pa = cc_info->cpuid_phys;
    > + sev_snp_cpuid_sz = cc_info->cpuid_len;

    You can do those assignments ...

    > +
    > + /*
    > + * These should always be valid values for SNP, even if guest isn't
    > + * actually configured to use the CPUID table.
    > + */
    > + if (!sev_snp_cpuid_pa || sev_snp_cpuid_sz < PAGE_SIZE)
    > + sev_es_terminate(1, GHCB_TERM_CPUID);


    ... here, after you've verified them.

    > +
    > + cpuid_info = (const struct sev_snp_cpuid_info *)sev_snp_cpuid_pa;
    > +
    > + /*
    > + * We should be able to trust the 'count' value in the CPUID table
    > + * area, but ensure it agrees with CC blob value to be safe.
    > + */
    > + if (sev_snp_cpuid_sz < (sizeof(struct sev_snp_cpuid_info) +
    > + sizeof(struct sev_snp_cpuid_fn) *
    > + cpuid_info->count))

    Yah, this is the type of paranoia I'm talking about!

    > + sev_es_terminate(1, GHCB_TERM_CPUID);
    > +
    > + sev_snp_cpuid_enabled = 1;
    > +}
    > diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
    > index ddf8ced4a879..d7b6f7420551 100644
    > --- a/arch/x86/kernel/sev.c
    > +++ b/arch/x86/kernel/sev.c
    > @@ -19,6 +19,8 @@
    > #include <linux/kernel.h>
    > #include <linux/mm.h>
    > #include <linux/cpumask.h>
    > +#include <linux/log2.h>
    > +#include <linux/efi.h>
    >
    > #include <asm/cpu_entry_area.h>
    > #include <asm/stacktrace.h>
    > @@ -32,6 +34,8 @@
    > #include <asm/smp.h>
    > #include <asm/cpu.h>
    > #include <asm/apic.h>
    > +#include <asm/efi.h>
    > +#include <asm/cpuid.h>
    >
    > #include "sev-internal.h"

    What are those includes for?

    Looks like a leftover...

    --
    Regards/Gruss,
    Boris.

    https://people.kernel.org/tglx/notes-about-netiquette

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