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Date: Tue, 14 Jul 2020 14:08:42 +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 <sean.j.christopherson@...el.com>,
Martin Radev <martin.b.radev@...il.com>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
virtualization@...ts.linux-foundation.org
Subject: [PATCH v4 40/75] x86/sev-es: Setup early #VC handler
From: Joerg Roedel <jroedel@...e.de>
Setup an early handler for #VC exceptions. There is no GHCB mapped
yet, so just re-use the vc_no_ghcb_handler. It can only handle CPUID
exit-codes, but that should be enough to get the kernel through
verify_cpu() and __startup_64() until it runs on virtual addresses.
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
arch/x86/include/asm/processor.h | 1 +
arch/x86/include/asm/sev-es.h | 3 +++
arch/x86/kernel/head64.c | 31 +++++++++++++++++++++++++
arch/x86/kernel/head_64.S | 39 ++++++++++++++++++++++++++++++++
4 files changed, 74 insertions(+)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 03b7c4ca425a..e6a029b76b3d 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -756,6 +756,7 @@ extern int sysenter_setup(void);
/* Defined in head.S */
extern struct desc_ptr early_gdt_descr;
+extern struct desc_ptr early_idt_descr;
extern void switch_to_new_gdt(int);
extern void load_direct_gdt(int);
diff --git a/arch/x86/include/asm/sev-es.h b/arch/x86/include/asm/sev-es.h
index 7c0807b84546..ec0e112a742b 100644
--- a/arch/x86/include/asm/sev-es.h
+++ b/arch/x86/include/asm/sev-es.h
@@ -73,4 +73,7 @@ static inline u64 lower_bits(u64 val, unsigned int bits)
return (val & mask);
}
+/* Early IDT entry points for #VC handler */
+extern void vc_no_ghcb(void);
+
#endif
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 32080e34ba92..9ea8a0437b66 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -38,6 +38,7 @@
#include <asm/fixmap.h>
#include <asm/extable.h>
#include <asm/trapnr.h>
+#include <asm/sev-es.h>
/*
* Manage page tables very early on.
@@ -537,3 +538,33 @@ void __head early_idt_setup_early_handler(unsigned long descr_addr, unsigned lon
native_write_idt_entry(idt, i, &desc);
}
}
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+static void __head set_early_idt_handler(gate_desc *idt, int n, void *handler)
+{
+ struct idt_data data;
+ gate_desc desc;
+
+ init_idt_data(&data, n, handler);
+ idt_init_desc(&desc, &data);
+ native_write_idt_entry(idt, n, &desc);
+}
+#endif
+
+void __head early_idt_setup(struct desc_ptr *descr, unsigned long physbase)
+{
+ gate_desc *idt = (gate_desc *)descr->address;
+ void __maybe_unused *handler;
+
+ idt = fixup_pointer(idt, physbase);
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+ /* VMM Communication Exception */
+ handler = fixup_pointer(vc_no_ghcb, physbase);
+ set_early_idt_handler(idt, X86_TRAP_VC, handler);
+#endif
+
+ /* Initialize IDT descriptor and load IDT */
+ early_idt_descr.address = (unsigned long)idt;
+ native_load_idt(&early_idt_descr);
+}
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 86473d49619d..3bd4c36d1d36 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -93,6 +93,15 @@ SYM_CODE_START_NOALIGN(startup_64)
.Lon_kernel_cs:
UNWIND_HINT_EMPTY
+ /* Setup IDT - Needed for SEV-ES */
+ pushq %rsi
+ /* early_idt_setup - first parameter */
+ leaq idt_descr(%rip), %rdi
+ /* early_idt_setup - second parameter */
+ leaq _text(%rip), %rsi
+ call early_idt_setup
+ popq %rsi
+
/* Sanitize CPU configuration */
call verify_cpu
@@ -382,6 +391,33 @@ SYM_CODE_START_LOCAL(early_idt_handler_common)
jmp restore_regs_and_return_to_kernel
SYM_CODE_END(early_idt_handler_common)
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+/*
+ * VC Exception handler used during very early boot. The
+ * early_idt_handler_array can't be used because it returns via the
+ * paravirtualized INTERRUPT_RETURN and pv-ops don't work that early.
+ */
+SYM_CODE_START_NOALIGN(vc_no_ghcb)
+ UNWIND_HINT_IRET_REGS offset=8
+
+ /* Build pt_regs */
+ PUSH_AND_CLEAR_REGS
+
+ /* Call C handler */
+ movq %rsp, %rdi
+ movq ORIG_RAX(%rsp), %rsi
+ call do_vc_no_ghcb
+
+ /* Unwind pt_regs */
+ POP_REGS
+
+ /* Remove Error Code */
+ addq $8, %rsp
+
+ /* Pure iret required here - don't use INTERRUPT_RETURN */
+ iretq
+SYM_CODE_END(vc_no_ghcb)
+#endif
#define SYM_DATA_START_PAGE_ALIGNED(name) \
SYM_START(name, SYM_L_GLOBAL, .balign PAGE_SIZE)
@@ -523,6 +559,9 @@ SYM_DATA_END(level1_fixmap_pgt)
SYM_DATA(early_gdt_descr, .word GDT_ENTRIES*8-1)
SYM_DATA_LOCAL(early_gdt_descr_base, .quad INIT_PER_CPU_VAR(gdt_page))
+SYM_DATA(early_idt_descr, .word NUM_EXCEPTION_VECTORS * 16)
+SYM_DATA_LOCAL(early_idt_descr_base, .quad 0)
+
.align 16
/* This must match the first entry in level2_kernel_pgt */
SYM_DATA(phys_base, .quad 0x0)
--
2.27.0
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