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SubjectRe: [PATCH v3 02/14] x86/sev: Make the VMPL0 checking function more generic
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On 3/25/2024 11:26 PM, Tom Lendacky wrote:
> Currently, the enforce_vmpl0() function uses a set argument when testing
> for VMPL0 and terminates the guest if the guest is not running at VMPL0.
>
> Make the function more generic by moving it into the common code, renaming
> it, allowing it to take an argument for use in the VMPL0 check (RMPADJUST
> instruction) and return the result of the check, allowing the caller to
> determine the action taken based on the result.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>

This is preparatory patch for patch3.

Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>

> ---
> arch/x86/boot/compressed/sev.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> index 5ad0ff4664f1..49dc9661176d 100644
> --- a/arch/x86/boot/compressed/sev.c
> +++ b/arch/x86/boot/compressed/sev.c
> @@ -335,10 +335,9 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
> sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
> }
>
> -static void enforce_vmpl0(void)
> +static bool running_at_vmpl0(void *va)
> {
> u64 attrs;
> - int err;
>
> /*
> * RMPADJUST modifies RMP permissions of a lesser-privileged (numerically
> @@ -347,12 +346,11 @@ static void enforce_vmpl0(void)
> *
> * If the guest is running at VMPL0, it will succeed. Even if that operation
> * modifies permission bits, it is still ok to do so currently because Linux
> - * SNP guests are supported only on VMPL0 so VMPL1 or higher permission masks
> - * changing is a don't-care.
> + * SNP guests running at VMPL0 only run at VMPL0, so VMPL1 or higher
> + * permission mask changes are a don't-care.
> */
> attrs = 1;
> - if (rmpadjust((unsigned long)&boot_ghcb_page, RMP_PG_SIZE_4K, attrs))
> - sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_NOT_VMPL0);
> + return !rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
> }
>
> /*
> @@ -588,7 +586,8 @@ void sev_enable(struct boot_params *bp)
> if (!(get_hv_features() & GHCB_HV_FT_SNP))
> sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
>
> - enforce_vmpl0();
> + if (!running_at_vmpl0(&boot_ghcb_page))
> + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_NOT_VMPL0);
> }
>
> if (snp && !(sev_status & MSR_AMD64_SEV_SNP_ENABLED))


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