[PATCH v6 07/22] x86/sev: Share implementation of MSR-based page state change

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

Both the decompressor and the SEV startup code implement the exact same
sequence for invoking the MSR based communication protocol to effectuate
a page state change.

Before tweaking the internal APIs used in both versions, merge them and
share them so those tweaks are only needed in a single place.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/boot/compressed/sev.c      | 40 ++------------------
 arch/x86/boot/startup/sev-shared.c  | 35 +++++++++++++++++
 arch/x86/boot/startup/sev-startup.c | 29 +-------------
 3 files changed, 39 insertions(+), 65 deletions(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 6c0f91d38595..f714235d3222 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -60,46 +60,12 @@ static bool sev_snp_enabled(void)
 	return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
 }
 
-static void __page_state_change(unsigned long paddr, enum psc_op op)
-{
-	u64 val, msr;
-
-	/*
-	 * If private -> shared then invalidate the page before requesting the
-	 * state change in the RMP table.
-	 */
-	if (op == SNP_PAGE_STATE_SHARED)
-		pvalidate_4k_page(paddr, paddr, false);
-
-	/* Save the current GHCB MSR value */
-	msr = sev_es_rd_ghcb_msr();
-
-	/* 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(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
-
-	/* Restore the GHCB MSR value */
-	sev_es_wr_ghcb_msr(msr);
-
-	/*
-	 * Now that page state is changed in the RMP table, validate it so that it is
-	 * consistent with the RMP entry.
-	 */
-	if (op == SNP_PAGE_STATE_PRIVATE)
-		pvalidate_4k_page(paddr, paddr, true);
-}
-
 void snp_set_page_private(unsigned long paddr)
 {
 	if (!sev_snp_enabled())
 		return;
 
-	__page_state_change(paddr, SNP_PAGE_STATE_PRIVATE);
+	__page_state_change(paddr, paddr, SNP_PAGE_STATE_PRIVATE);
 }
 
 void snp_set_page_shared(unsigned long paddr)
@@ -107,7 +73,7 @@ void snp_set_page_shared(unsigned long paddr)
 	if (!sev_snp_enabled())
 		return;
 
-	__page_state_change(paddr, SNP_PAGE_STATE_SHARED);
+	__page_state_change(paddr, paddr, SNP_PAGE_STATE_SHARED);
 }
 
 bool early_setup_ghcb(void)
@@ -133,7 +99,7 @@ bool early_setup_ghcb(void)
 void snp_accept_memory(phys_addr_t start, phys_addr_t end)
 {
 	for (phys_addr_t pa = start; pa < end; pa += PAGE_SIZE)
-		__page_state_change(pa, SNP_PAGE_STATE_PRIVATE);
+		__page_state_change(pa, pa, SNP_PAGE_STATE_PRIVATE);
 }
 
 void sev_es_shutdown_ghcb(void)
diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c
index 852c8443ed1a..1da1afa8677a 100644
--- a/arch/x86/boot/startup/sev-shared.c
+++ b/arch/x86/boot/startup/sev-shared.c
@@ -653,6 +653,41 @@ static void __head pvalidate_4k_page(unsigned long vaddr, unsigned long paddr,
 	}
 }
 
+static void __head __page_state_change(unsigned long vaddr, unsigned long paddr,
+				       enum psc_op op)
+{
+	u64 val, msr;
+
+	/*
+	 * If private -> shared then invalidate the page before requesting the
+	 * state change in the RMP table.
+	 */
+	if (op == SNP_PAGE_STATE_SHARED)
+		pvalidate_4k_page(vaddr, paddr, false);
+
+	/* Save the current GHCB MSR value */
+	msr = sev_es_rd_ghcb_msr();
+
+	/* 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(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
+
+	/* Restore the GHCB MSR value */
+	sev_es_wr_ghcb_msr(msr);
+
+	/*
+	 * Now that page state is changed in the RMP table, validate it so that it is
+	 * consistent with the RMP entry.
+	 */
+	if (op == SNP_PAGE_STATE_PRIVATE)
+		pvalidate_4k_page(vaddr, paddr, true);
+}
+
 /*
  * Maintain the GPA of the SVSM Calling Area (CA) in order to utilize the SVSM
  * services needed when not running in VMPL0.
diff --git a/arch/x86/boot/startup/sev-startup.c b/arch/x86/boot/startup/sev-startup.c
index 8a06f6026101..5eb7d939ebd3 100644
--- a/arch/x86/boot/startup/sev-startup.c
+++ b/arch/x86/boot/startup/sev-startup.c
@@ -135,7 +135,6 @@ early_set_pages_state(unsigned long vaddr, unsigned long paddr,
 		      unsigned long npages, enum psc_op op)
 {
 	unsigned long paddr_end;
-	u64 val;
 
 	vaddr = vaddr & PAGE_MASK;
 
@@ -143,37 +142,11 @@ early_set_pages_state(unsigned long vaddr, unsigned long paddr,
 	paddr_end = paddr + (npages << PAGE_SHIFT);
 
 	while (paddr < paddr_end) {
-		/* Page validation must be rescinded before changing to shared */
-		if (op == SNP_PAGE_STATE_SHARED)
-			pvalidate_4k_page(vaddr, paddr, false);
-
-		/*
-		 * Use the MSR protocol because this function can be called before
-		 * the GHCB is established.
-		 */
-		sev_es_wr_ghcb_msr(GHCB_MSR_PSC_REQ_GFN(paddr >> PAGE_SHIFT, op));
-		VMGEXIT();
-
-		val = sev_es_rd_ghcb_msr();
-
-		if (GHCB_RESP_CODE(val) != GHCB_MSR_PSC_RESP)
-			goto e_term;
-
-		if (GHCB_MSR_PSC_RESP_VAL(val))
-			goto e_term;
-
-		/* Page validation must be performed after changing to private */
-		if (op == SNP_PAGE_STATE_PRIVATE)
-			pvalidate_4k_page(vaddr, paddr, true);
+		__page_state_change(vaddr, paddr, op);
 
 		vaddr += PAGE_SIZE;
 		paddr += PAGE_SIZE;
 	}
-
-	return;
-
-e_term:
-	sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
 }
 
 void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
-- 
2.50.0.727.gbf7dc18ff4-goog