linux-kernel - [RFC PATCH 06/12] x86/sev: Cache AP Jump Table Address

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Date:   Mon,  5 Jul 2021 10:24:37 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
        hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Martin Radev <martin.b.radev@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: [RFC PATCH 06/12] x86/sev: Cache AP Jump Table Address

From: Joerg Roedel <jroedel@...e.de>

Store the physical address of the AP Jump Table in kernel memory so
that it does not need to be fetched from the Hypervisor again.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/kernel/sev.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 5d3422e8b25e..eedba56b6bac 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -42,6 +42,9 @@ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);
  */
 static struct ghcb __initdata *boot_ghcb;
 
+/* Cached AP Jump Table Address */
+static phys_addr_t sev_es_jump_table_pa;
+
 /* #VC handler runtime per-CPU data */
 struct sev_es_runtime_data {
 	struct ghcb ghcb_page;
@@ -546,12 +549,14 @@ void noinstr __sev_es_nmi_complete(void)
 	__sev_put_ghcb(&state);
 }
 
-static u64 get_jump_table_addr(void)
+static phys_addr_t get_jump_table_addr(void)
 {
 	struct ghcb_state state;
 	unsigned long flags;
 	struct ghcb *ghcb;
-	u64 ret = 0;
+
+	if (sev_es_jump_table_pa)
+		return sev_es_jump_table_pa;
 
 	local_irq_save(flags);
 
@@ -567,39 +572,36 @@ static u64 get_jump_table_addr(void)
 
 	if (ghcb_sw_exit_info_1_is_valid(ghcb) &&
 	    ghcb_sw_exit_info_2_is_valid(ghcb))
-		ret = ghcb->save.sw_exit_info_2;
+		sev_es_jump_table_pa = (phys_addr_t)ghcb->save.sw_exit_info_2;
 
 	__sev_put_ghcb(&state);
 
 	local_irq_restore(flags);
 
-	return ret;
+	return sev_es_jump_table_pa;
 }
 
 int sev_es_setup_ap_jump_table(struct real_mode_header *rmh)
 {
 	u16 startup_cs, startup_ip;
-	phys_addr_t jump_table_pa;
-	u64 jump_table_addr;
 	u16 __iomem *jump_table;
+	phys_addr_t pa;
 
-	jump_table_addr = get_jump_table_addr();
+	pa = get_jump_table_addr();
 
 	/* On UP guests there is no jump table so this is not a failure */
-	if (!jump_table_addr)
+	if (!pa)
 		return 0;
 
 	/* Check if AP Jump Table is page-aligned */
-	if (jump_table_addr & ~PAGE_MASK)
+	if (pa & ~PAGE_MASK)
 		return -EINVAL;
 
-	jump_table_pa = jump_table_addr & PAGE_MASK;
-
 	startup_cs = (u16)(rmh->trampoline_start >> 4);
 	startup_ip = (u16)(rmh->sev_es_trampoline_start -
 			   rmh->trampoline_start);
 
-	jump_table = ioremap_encrypted(jump_table_pa, PAGE_SIZE);
+	jump_table = ioremap_encrypted(pa, PAGE_SIZE);
 	if (!jump_table)
 		return -EIO;
 
-- 
2.31.1