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    SubjectRE: [PATCH V6 2/5] x86/hyper-v: Add hyperv Isolation VM check in the cc_platform_has()
    Date
    From: Tianyu Lan <ltykernel@gmail.com> Sent: Monday, December 6, 2021 11:56 PM
    >
    > Hyper-V provides Isolation VM which has memory encrypt support. Add
    > hyperv_cc_platform_has() and return true for check of GUEST_MEM_ENCRYPT
    > attribute.
    >
    > Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
    > ---
    > Change since v3:
    > * Change code style of checking GUEST_MEM attribute in the
    > hyperv_cc_platform_has().
    > ---
    > arch/x86/kernel/cc_platform.c | 8 ++++++++
    > 1 file changed, 8 insertions(+)
    >
    > diff --git a/arch/x86/kernel/cc_platform.c b/arch/x86/kernel/cc_platform.c
    > index 03bb2f343ddb..47db88c275d5 100644
    > --- a/arch/x86/kernel/cc_platform.c
    > +++ b/arch/x86/kernel/cc_platform.c
    > @@ -11,6 +11,7 @@
    > #include <linux/cc_platform.h>
    > #include <linux/mem_encrypt.h>
    >
    > +#include <asm/mshyperv.h>
    > #include <asm/processor.h>
    >
    > static bool __maybe_unused intel_cc_platform_has(enum cc_attr attr)
    > @@ -58,9 +59,16 @@ static bool amd_cc_platform_has(enum cc_attr attr)
    > #endif
    > }
    >
    > +static bool hyperv_cc_platform_has(enum cc_attr attr)
    > +{
    > + return attr == CC_ATTR_GUEST_MEM_ENCRYPT;
    > +}
    >
    > bool cc_platform_has(enum cc_attr attr)
    > {
    > + if (hv_is_isolation_supported())
    > + return hyperv_cc_platform_has(attr);
    > +
    > if (sme_me_mask)
    > return amd_cc_platform_has(attr);
    >

    Throughout Linux kernel code, there are about 20 calls to cc_platform_has()
    with CC_ATTR_GUEST_MEM_ENCRYPT as the argument. The original code
    (from v1 of this patch set) only dealt with the call in sev_setup_arch(). But
    with this patch, all the other calls that previously returned "false" will now
    return "true" in a Hyper-V Isolated VM. I didn't try to analyze all these other
    calls, so I think there's an open question about whether this is the behavior
    we want.

    Michael

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