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Message-ID: <SA1PR21MB13357B3CC486514D2DF50A4DBF139@SA1PR21MB1335.namprd21.prod.outlook.com>
Date: Mon, 28 Nov 2022 19:37:59 +0000
From: Dexuan Cui <decui@...rosoft.com>
To: Dave Hansen <dave.hansen@...el.com>,
"Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
"ak@...ux.intel.com" <ak@...ux.intel.com>,
"arnd@...db.de" <arnd@...db.de>, "bp@...en8.de" <bp@...en8.de>,
"brijesh.singh@....com" <brijesh.singh@....com>,
"Williams, Dan J" <dan.j.williams@...el.com>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
"hpa@...or.com" <hpa@...or.com>,
"jane.chu@...cle.com" <jane.chu@...cle.com>,
"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
KY Srinivasan <kys@...rosoft.com>,
"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"luto@...nel.org" <luto@...nel.org>,
"mingo@...hat.com" <mingo@...hat.com>,
"peterz@...radead.org" <peterz@...radead.org>,
"rostedt@...dmis.org" <rostedt@...dmis.org>,
"sathyanarayanan.kuppuswamy@...ux.intel.com"
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
"seanjc@...gle.com" <seanjc@...gle.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"tony.luck@...el.com" <tony.luck@...el.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
"x86@...nel.org" <x86@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 5/6] x86/hyperv: Support hypercalls for TDX guests
> From: Dave Hansen <dave.hansen@...el.com>
> Sent: Monday, November 28, 2022 11:11 AM
> On 11/28/22 11:03, Dexuan Cui wrote:
> ...
> > u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
> > {
> > struct tdx_hypercall_args args = { };
> >
> > if (!(control & HV_HYPERCALL_FAST_BIT)) {
> > if (param1)
> > param1 = cc_mkdec(param1);
> >
> > if (param2)
> > param2 = cc_mkdec(param2);
> > }
> >
> > args.r10 = control;
> > args.rdx = param1;
> > args.r8 = param2;
> >
> > (void)__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT);
> >
> > return args.r11;
> > }
>
> I still think this is problematic.
>
> The cc_mkdec() should be done on the parameters when the code still
> *knows* that they are addresses.
Makes sense.
> How do we know, for instance, that no hypercall using this interface
> will *ever* take the 0x0 physical address as an argument?
A 0x0 physical address as an argument still works: the 0 is passed
to the hypervisor using GHCI. I believe Hyper-V interprets the 0 as
an error (if the param is needed), and returns an "invalid parameter"
error code to the guest.
Here is the updated version:
diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 70170049be2c..41395891d112 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -242,6 +242,20 @@ bool hv_isolation_type_tdx(void)
{
return static_branch_unlikely(&isolation_type_tdx);
}
+
+u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
+{
+ struct tdx_hypercall_args args = { };
+
+ args.r10 = control;
+ args.rdx = param1;
+ args.r8 = param2;
+
+ (void)__tdx_hypercall(&args, TDX_HCALL_HAS_OUTPUT);
+
+ return args.r11;
+}
+EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
#endif
/*
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 9cc6db45c3bc..ea053af067a2 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -10,6 +10,7 @@
#include <asm/nospec-branch.h>
#include <asm/paravirt.h>
#include <asm/mshyperv.h>
+#include <asm/coco.h>
union hv_ghcb;
@@ -39,6 +40,8 @@ int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
+u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2);
+
static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
{
u64 input_address = input ? virt_to_phys(input) : 0;
@@ -46,6 +49,12 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
u64 hv_status;
#ifdef CONFIG_X86_64
+ if (hv_isolation_type_tdx()) {
+ u64 param1 = input_address ? cc_mkdec(input_address) : 0;
+ u64 param2 = output_address ? cc_mkdec(output_address) : 0;
+ return hv_tdx_hypercall(control, param1, param2);
+ }
+
if (!hv_hypercall_pg)
return U64_MAX;
@@ -83,6 +92,9 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;
#ifdef CONFIG_X86_64
+ if (hv_isolation_type_tdx())
+ return hv_tdx_hypercall(control, input1, 0);
+
{
__asm__ __volatile__(CALL_NOSPEC
: "=a" (hv_status), ASM_CALL_CONSTRAINT,
@@ -114,6 +126,9 @@ static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;
#ifdef CONFIG_X86_64
+ if (hv_isolation_type_tdx())
+ return hv_tdx_hypercall(control, input1, input2);
+
{
__asm__ __volatile__("mov %4, %%r8\n"
CALL_NOSPEC
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