Commit 68a501d7 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Borislav Petkov (AMD)
Browse files

x86/boot: Drop redundant RMPADJUST in SEV SVSM presence check 



snp_vmpl will be assigned a non-zero value when executing at a VMPL other than
0, and this is inferred from a call to RMPADJUST, which only works when
running at VMPL0.

This means that testing snp_vmpl is sufficient, and there is no need to
perform the same check again.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250828102202.1849035-34-ardb+git@google.com
parent c54604fb

arch/x86/boot/compressed/sev.c

+3 −17
Original line number Diff line number Diff line
@@ -406,30 +406,16 @@ void sev_enable(struct boot_params *bp) 
	 */

	if (sev_status & MSR_AMD64_SEV_SNP_ENABLED) {

		u64 hv_features;

		int ret;



		hv_features = get_hv_features();

		if (!(hv_features & GHCB_HV_FT_SNP))

			sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);



		/*

		 * Enforce running at VMPL0 or with an SVSM.

		 *

		 * Use RMPADJUST (see the rmpadjust() function for a description of

		 * what the instruction does) to update the VMPL1 permissions of a

		 * page. If the guest is running at VMPL0, this will succeed. If the

		 * guest is running at any other VMPL, this will fail. Linux SNP guests

		 * only ever run at a single VMPL level so permission mask changes of a

		 * lesser-privileged VMPL are a don't-care.

		 */

		ret = rmpadjust((unsigned long)&boot_ghcb_page, RMP_PG_SIZE_4K, 1);



		/*

		 * Running at VMPL0 is not required if an SVSM is present and the hypervisor

		 * supports the required SVSM GHCB events.

		 * Running at VMPL0 is required unless an SVSM is present and

		 * the hypervisor supports the required SVSM GHCB events.

		 */

		if (ret &&

		    !(snp_vmpl && (hv_features & GHCB_HV_FT_SNP_MULTI_VMPL)))

		if (snp_vmpl && !(hv_features & GHCB_HV_FT_SNP_MULTI_VMPL))

			sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_NOT_VMPL0);

	}