linux-kernel - [RFC PATCH] x86/sev: Cleanup vc_handle

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Message-ID: <20241106172647.GAZyum1zngPDwyD2IJ@fat_crate.local>
Date: Wed, 6 Nov 2024 18:26:47 +0100
From: "Borislav Petkov (AMD)" <bp@...en8.de>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: x86-ml <x86@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
	linux-coco@...ts.linux.dev
Subject: [RFC PATCH] x86/sev: Cleanup vc_handle_msr()

Hi,

I think we should clean this one up before in-flight patchsets make it more
unreadable and in need for an even more cleanup.

---
Carve out the MSR_SVSM_CAA into a helper with the suggestion that
upcoming future users should do the same. Rename that silly exit_info_1
into what it actually means in this function - whether the MSR access is
a read or a write.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
---
 arch/x86/coco/sev/core.c | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 97f445f3366a..1efb4a5c5ab3 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -1406,35 +1406,39 @@ int __init sev_es_efi_map_ghcbs(pgd_t *pgd)
 	return 0;
 }
 
+/* Writes to the SVSM CAA MSR are ignored */
+static enum es_result __vc_handle_msr_caa(struct pt_regs *regs, bool write)
+{
+	if (write)
+		return ES_OK;
+
+	regs->ax = lower_32_bits(this_cpu_read(svsm_caa_pa));
+	regs->dx = upper_32_bits(this_cpu_read(svsm_caa_pa));
+
+	return ES_OK;
+}
+
 static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 {
 	struct pt_regs *regs = ctxt->regs;
 	enum es_result ret;
-	u64 exit_info_1;
+	bool write;
 
 	/* Is it a WRMSR? */
-	exit_info_1 = (ctxt->insn.opcode.bytes[1] == 0x30) ? 1 : 0;
-
-	if (regs->cx == MSR_SVSM_CAA) {
-		/* Writes to the SVSM CAA msr are ignored */
-		if (exit_info_1)
-			return ES_OK;
-
-		regs->ax = lower_32_bits(this_cpu_read(svsm_caa_pa));
-		regs->dx = upper_32_bits(this_cpu_read(svsm_caa_pa));
+	write = ctxt->insn.opcode.bytes[1] == 0x30;
 
-		return ES_OK;
-	}
+	if (regs->cx == MSR_SVSM_CAA)
+		return __vc_handle_msr_caa(regs, write);
 
 	ghcb_set_rcx(ghcb, regs->cx);
-	if (exit_info_1) {
+	if (write) {
 		ghcb_set_rax(ghcb, regs->ax);
 		ghcb_set_rdx(ghcb, regs->dx);
 	}
 
-	ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_MSR, exit_info_1, 0);
+	ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_MSR, !!write, 0);
 
-	if ((ret == ES_OK) && (!exit_info_1)) {
+	if ((ret == ES_OK) && (!write)) {
 		regs->ax = ghcb->save.rax;
 		regs->dx = ghcb->save.rdx;
 	}
-- 
2.43.0


-- 
Regards/Gruss,
    Boris.

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