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SubjectRe: [RFC v2-fix-v2 1/1] x86: Introduce generic protected guest abstraction
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On 6/3/21 11:14 AM, Borislav Petkov wrote:
> On Tue, Jun 01, 2021 at 02:14:17PM -0700, Kuppuswamy Sathyanarayanan wrote:
>> diff --git a/include/linux/protected_guest.h b/include/linux/protected_guest.h
>> new file mode 100644
>> index 000000000000..303dfba81d52
>> --- /dev/null
>> +++ b/include/linux/protected_guest.h
>> @@ -0,0 +1,40 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +#ifndef _LINUX_PROTECTED_GUEST_H
>> +#define _LINUX_PROTECTED_GUEST_H 1
>> +
>> +#include <linux/mem_encrypt.h>
>> +
>> +/* Protected Guest Feature Flags (leave 0-0xff for arch specific flags) */
>> +
>> +/* Support for guest encryption */
>> +#define VM_MEM_ENCRYPT 0x100
>> +/* Encryption support is active */
>> +#define VM_MEM_ENCRYPT_ACTIVE 0x101
>> +/* Support for unrolled string IO */
>> +#define VM_UNROLL_STRING_IO 0x102
>> +/* Support for host memory encryption */
>> +#define VM_HOST_MEM_ENCRYPT 0x103
>> +/* Support for shared mapping initialization (after early init) */
>> +#define VM_SHARED_MAPPING_INIT 0x104
>
> Ok, a couple of things:
>
> first of all, those flags with that VM_ prefix make me think of
> "virtual memory" instead of "virtual machine". So they should be
> something else, like, say
>
> PR_G_... for Protected Guest or so. Or PR_GUEST or ...

I would prefer PR_GUEST over PR_G_

>
> (yeah, good namespaces are all taken. )
>
> Then, about the function name length, I'm fine if we did:
>
> prot_guest_has()
>
> or something even shorter, if you folks have a good suggestion.
>
> Anyway, below is a diff ontop of your tree with what I think the
> barebones of this should be.
>
> As a reply to this message I went and converted sme_active() to use
> protected_guest_has() too.
>
> Comments, complaints?
>
> Thx.
>
> ---
> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> index 1492b0eb29d0..9c80c68d75b5 100644
> --- a/arch/x86/include/asm/mem_encrypt.h
> +++ b/arch/x86/include/asm/mem_encrypt.h
> @@ -56,8 +56,6 @@ bool sev_es_active(void);
>
> #define __bss_decrypted __section(".bss..decrypted")
>
> -bool amd_protected_guest_has(unsigned long flag);
> -
> #else /* !CONFIG_AMD_MEM_ENCRYPT */
>
> #define sme_me_mask 0ULL
> @@ -88,8 +86,6 @@ early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0;
>
> static inline void mem_encrypt_free_decrypted_mem(void) { }
>
> -static inline bool amd_protected_guest_has(unsigned long flag) { return false; }
> -
> #define __bss_decrypted
>
> #endif /* CONFIG_AMD_MEM_ENCRYPT */
> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> index fa5cd05d3b5b..f09996c6a272 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/pgtable_types.h>
>
> #define GHCB_PROTO_OUR 0x0001UL
> #define GHCB_PROTOCOL_MAX 1ULL
> @@ -81,12 +82,15 @@ static __always_inline void sev_es_nmi_complete(void)
> __sev_es_nmi_complete();
> }
> extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
> +bool sev_protected_guest_has(unsigned long flag);
> +
> #else
> static inline void sev_es_ist_enter(struct pt_regs *regs) { }
> static inline void sev_es_ist_exit(void) { }
> static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; }
> static inline void sev_es_nmi_complete(void) { }
> static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
> +static inline bool sev_protected_guest_has(unsigned long flag) { return false; }
> #endif
>
> -#endif
> +#endif /* __ASM_ENCRYPTED_STATE_H */
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index f7a743d122eb..01a224fdb897 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -1402,3 +1402,14 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs)
> while (true)
> halt();
> }
> +
> +bool sev_protected_guest_has(unsigned long flag)
> +{
> + switch (flag) {
> + case VM_MEM_ENCRYPT:
> + case VM_MEM_ENCRYPT_ACTIVE:
> + return true;
> + }
> +
> + return false;
> +}

I assume this file will get compiled for both SEV and SME cases.

> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index ced658e79753..49d11bb6e02a 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -391,18 +391,6 @@ bool noinstr sev_es_active(void)
> return sev_status & MSR_AMD64_SEV_ES_ENABLED;
> }
>
> -bool amd_protected_guest_has(unsigned long flag)
> -{
> - switch (flag) {
> - case VM_MEM_ENCRYPT:
> - case VM_MEM_ENCRYPT_ACTIVE:
> - return true;
> - }
> -
> - return false;
> -}
> -EXPORT_SYMBOL_GPL(amd_protected_guest_has);
> -
> /* Override for DMA direct allocation check - AMD specific initialization */
> bool amd_force_dma_unencrypted(struct device *dev)
> {
> diff --git a/include/linux/protected_guest.h b/include/linux/protected_guest.h
> index 6855d5b3e244..bb4b1a06b21f 100644
> --- a/include/linux/protected_guest.h
> +++ b/include/linux/protected_guest.h
> @@ -2,7 +2,9 @@
> #ifndef _LINUX_PROTECTED_GUEST_H
> #define _LINUX_PROTECTED_GUEST_H 1
>
> -#include <linux/mem_encrypt.h>
> +#include <asm/processor.h>
> +#include <asm/tdx.h>
> +#include <asm/sev.h>
>
> /* Protected Guest Feature Flags (leave 0-0xff for arch specific flags) */
>
> @@ -20,23 +22,18 @@
> #define VM_DISABLE_UNCORE_SUPPORT 0x105
>
> #if defined(CONFIG_INTEL_TDX_GUEST) || defined(CONFIG_AMD_MEM_ENCRYPT)
> -
> -#include <asm/tdx.h>
> -
> static inline bool protected_guest_has(unsigned long flag)
> {
> if (is_tdx_guest())
> return tdx_protected_guest_has(flag);
> - else if (mem_encrypt_active())
> - return amd_protected_guest_has(flag);
> + else if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
> + return sev_protected_guest_has(flag);

Since you are checking for AMD vendor ID, why not use amd_protected_guest_has()?

>
> return false;
> }
>
> #else
> -
> static inline bool protected_guest_has(unsigned long flag) { return false; }
> -
> #endif
>
> -#endif
> +#endif /* _LINUX_PROTECTED_GUEST_H */
>
>

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer

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