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Message-Id: <651ceb5a89721621d522419e8a5d901632a78a22.1722019360.git.tim.merrifield@broadcom.com>
Date: Fri, 26 Jul 2024 18:58:00 +0000
From: Tim Merrifield <tim.merrifield@...adcom.com>
To: "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>,
x86@...nel.org,
"H . Peter Anvin" <hpa@...or.com>,
Xin Li <xin3.li@...el.com>,
Tim Merrifield <tim.merrifield@...adcom.com>,
Ard Biesheuvel <ardb@...nel.org>,
Kai Huang <kai.huang@...el.com>,
Kevin Loughlin <kevinloughlin@...gle.com>,
Thomas Zimmermann <tzimmermann@...e.de>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Kees Cook <kees@...nel.org>,
Mike Rapoport <rppt@...nel.org>,
Brian Gerst <brgerst@...il.com>,
linux-coco@...ts.linux.dev,
linux-kernel@...r.kernel.org,
Ajay Kaher <ajay.kaher@...adcom.com>,
Alexey Makhalov <alexey.makhalov@...adcom.com>,
Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
virtualization@...ts.linux.dev,
alex.james@...adcom.com,
doug.covelli@...adcom.com,
jeffrey.sheldon@...adcom.com,
kevin.christopher@...adcom.com,
aravind-as.srinivasan@...adcom.com,
ravindra.kumar@...adcom.com
Subject: [PATCH v2 1/2] Add prctl to allow userlevel TDX hypercalls
Add a new process-level prctl option to enable/disable user-level
hypercalls when running in a confidential VM. Add support for
checking this flag on VMCALL #VE for TDX and transfer control to
a hypervisor vendor-specific handler.
Signed-off-by: Tim Merrifield <tim.merrifield@...adcom.com>
---
arch/x86/coco/tdx/tdx.c | 23 +++++++++++++++++++++++
arch/x86/include/asm/mmu.h | 2 ++
arch/x86/include/asm/x86_init.h | 1 +
arch/x86/include/uapi/asm/prctl.h | 3 +++
arch/x86/kernel/process.c | 22 ++++++++++++++++++++++
5 files changed, 51 insertions(+)
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 078e2bac2553..02580fcf6157 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -238,6 +238,7 @@ static int ve_instr_len(struct ve_info *ve)
case EXIT_REASON_MSR_WRITE:
case EXIT_REASON_CPUID:
case EXIT_REASON_IO_INSTRUCTION:
+ case EXIT_REASON_VMCALL:
/* It is safe to use ve->instr_len for #VE due instructions */
return ve->instr_len;
case EXIT_REASON_EPT_VIOLATION:
@@ -634,6 +635,26 @@ void tdx_get_ve_info(struct ve_info *ve)
ve->instr_info = upper_32_bits(args.r10);
}
+/*
+ * Handle user-initiated, hypervisor-specific VMCALLs.
+ */
+static int handle_user_vmcall(struct pt_regs *regs, struct ve_info *ve)
+{
+ int err;
+
+ if (!x86_platform.hyper.tdx_hcall)
+ return -EOPNOTSUPP;
+
+ if (!test_bit(MM_CONTEXT_COCO_USER_HCALL, ¤t->mm->context.flags))
+ return -EOPNOTSUPP;
+
+ err = x86_platform.hyper.tdx_hcall(regs);
+ if (err)
+ return err;
+
+ return ve_instr_len(ve);
+}
+
/*
* Handle the user initiated #VE.
*
@@ -645,6 +666,8 @@ static int virt_exception_user(struct pt_regs *regs, struct ve_info *ve)
switch (ve->exit_reason) {
case EXIT_REASON_CPUID:
return handle_cpuid(regs, ve);
+ case EXIT_REASON_VMCALL:
+ return handle_user_vmcall(regs, ve);
default:
pr_warn("Unexpected #VE: %lld\n", ve->exit_reason);
return -EIO;
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index ce4677b8b735..626ab327e34c 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -16,6 +16,8 @@
#define MM_CONTEXT_LOCK_LAM 2
/* Allow LAM and SVA coexisting */
#define MM_CONTEXT_FORCE_TAGGED_SVA 3
+/* Allow COCO user-level hypercalls. */
+#define MM_CONTEXT_COCO_USER_HCALL 4
/*
* x86 has arch-specific MMU state beyond what lives in mm_struct.
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 213cf5379a5a..04d43b91d32a 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -282,6 +282,7 @@ struct x86_hyper_runtime {
void (*sev_es_hcall_prepare)(struct ghcb *ghcb, struct pt_regs *regs);
bool (*sev_es_hcall_finish)(struct ghcb *ghcb, struct pt_regs *regs);
bool (*is_private_mmio)(u64 addr);
+ int (*tdx_hcall)(struct pt_regs *regs);
};
/**
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index 384e2cc6ac19..37d154e503a3 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -16,6 +16,9 @@
#define ARCH_GET_XCOMP_GUEST_PERM 0x1024
#define ARCH_REQ_XCOMP_GUEST_PERM 0x1025
+#define ARCH_GET_COCO_USER_HCALL 0x1030
+#define ARCH_SET_COCO_USER_HCALL 0x1031
+
#define ARCH_XCOMP_TILECFG 17
#define ARCH_XCOMP_TILEDATA 18
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index f63f8fd00a91..198431919fd2 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -1042,6 +1042,24 @@ unsigned long __get_wchan(struct task_struct *p)
return addr;
}
+static int get_coco_user_hcall_mode(void)
+{
+ return !test_bit(MM_CONTEXT_COCO_USER_HCALL,
+ ¤t->mm->context.flags);
+}
+
+static int set_coco_user_hcall_mode(unsigned long enabled)
+{
+ if (enabled)
+ set_bit(MM_CONTEXT_COCO_USER_HCALL,
+ ¤t->mm->context.flags);
+ else
+ clear_bit(MM_CONTEXT_COCO_USER_HCALL,
+ ¤t->mm->context.flags);
+
+ return 0;
+}
+
long do_arch_prctl_common(int option, unsigned long arg2)
{
switch (option) {
@@ -1055,6 +1073,10 @@ long do_arch_prctl_common(int option, unsigned long arg2)
case ARCH_GET_XCOMP_GUEST_PERM:
case ARCH_REQ_XCOMP_GUEST_PERM:
return fpu_xstate_prctl(option, arg2);
+ case ARCH_GET_COCO_USER_HCALL:
+ return get_coco_user_hcall_mode();
+ case ARCH_SET_COCO_USER_HCALL:
+ return set_coco_user_hcall_mode(arg2);
}
return -EINVAL;
--
2.40.1
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