Re: [PATCH Part1 RFC v3 08/22] x86/compressed: Add helper for validating pages in the decompression stage

Borislav Petkov
2021-06-08T11:12:42Z

On Wed, Jun 02, 2021 at 09:04:02AM -0500, Brijesh Singh wrote:
> +static void __page_state_change(unsigned long paddr, int op)
> +{
> + u64 val;
> +
> + if (!sev_snp_enabled())
> + return;
> +
> + /*
> + * If private -> shared then invalidate the page before requesting the
> + * state change in the RMP table.
> + */
> + if ((op == SNP_PAGE_STATE_SHARED) && pvalidate(paddr, RMP_PG_SIZE_4K, 0))
> + goto e_pvalidate;
> +
> + /* Issue VMGEXIT to change the page state in RMP table. */
> + sev_es_wr_ghcb_msr(GHCB_MSR_PSC_REQ_GFN(paddr >> PAGE_SHIFT, op));
> + VMGEXIT();
> +
> + /* Read the response of the VMGEXIT. */
> + val = sev_es_rd_ghcb_msr();
> + if ((GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP) || GHCB_MSR_PSC_RESP_VAL(val))
> + sev_es_terminate(1, GHCB_TERM_PSC);
> +
> + /*
> + * Now that page is added in the RMP table, validate it so that it is
> + * consistent with the RMP entry.
> + */
> + if ((op == SNP_PAGE_STATE_PRIVATE) && pvalidate(paddr, RMP_PG_SIZE_4K, 1))
> + goto e_pvalidate;
> +
> + return;
> +
> +e_pvalidate:
> + sev_es_terminate(1, GHCB_TERM_PVALIDATE);
> +}

You don't even need that label, diff ontop:

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 808fe1f6b170..dd0f22386fd2 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -146,7 +146,7 @@ static void __page_state_change(unsigned long paddr, int op)
* state change in the RMP table.
*/
if ((op == SNP_PAGE_STATE_SHARED) && pvalidate(paddr, RMP_PG_SIZE_4K, 0))
- goto e_pvalidate;
+ sev_es_terminate(1, GHCB_TERM_PVALIDATE);

/* Issue VMGEXIT to change the page state in RMP table. */
sev_es_wr_ghcb_msr(GHCB_MSR_PSC_REQ_GFN(paddr >> PAGE_SHIFT, op));
@@ -162,12 +162,7 @@ static void __page_state_change(unsigned long paddr, int op)
* consistent with the RMP entry.
*/
if ((op == SNP_PAGE_STATE_PRIVATE) && pvalidate(paddr, RMP_PG_SIZE_4K, 1))
- goto e_pvalidate;
-
- return;
-
-e_pvalidate:
- sev_es_terminate(1, GHCB_TERM_PVALIDATE);
+ sev_es_terminate(1, GHCB_TERM_PVALIDATE);
}

void snp_set_page_private(unsigned long paddr)

--
Regards/Gruss,
Boris.