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Date: Thu, 2 Sep 2021 00:20:28 +0000
From: Michael Kelley <mikelley@...rosoft.com>
To: Tianyu Lan <ltykernel@...il.com>,
KY Srinivasan <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
Dexuan Cui <decui@...rosoft.com>,
"catalin.marinas@....com" <catalin.marinas@....com>,
"will@...nel.org" <will@...nel.org>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
"hpa@...or.com" <hpa@...or.com>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"luto@...nel.org" <luto@...nel.org>,
"peterz@...radead.org" <peterz@...radead.org>,
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"thomas.lendacky@....com" <thomas.lendacky@....com>,
Tianyu Lan <Tianyu.Lan@...rosoft.com>,
"pgonda@...gle.com" <pgonda@...gle.com>,
"martin.b.radev@...il.com" <martin.b.radev@...il.com>,
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CC: "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
vkuznets <vkuznets@...hat.com>,
"parri.andrea@...il.com" <parri.andrea@...il.com>,
"dave.hansen@...el.com" <dave.hansen@...el.com>
Subject: RE: [PATCH V4 06/13] hyperv: Add ghcb hvcall support for SNP VM
From: Tianyu Lan <ltykernel@...il.com> Sent: Friday, August 27, 2021 10:21 AM
>
Subject line tag should probably be "x86/hyperv:" since the majority
of the code added is under arch/x86.
> hyperv provides ghcb hvcall to handle VMBus
> HVCALL_SIGNAL_EVENT and HVCALL_POST_MESSAGE
> msg in SNP Isolation VM. Add such support.
>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> ---
> Change since v3:
> * Add hv_ghcb_hypercall() stub function to avoid
> compile error for ARM.
> ---
> arch/x86/hyperv/ivm.c | 71 ++++++++++++++++++++++++++++++++++
> drivers/hv/connection.c | 6 ++-
> drivers/hv/hv.c | 8 +++-
> drivers/hv/hv_common.c | 6 +++
> include/asm-generic/mshyperv.h | 1 +
> 5 files changed, 90 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index f56fe4f73000..e761c67e2218 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -17,10 +17,81 @@
> #include <asm/io.h>
> #include <asm/mshyperv.h>
>
> +#define GHCB_USAGE_HYPERV_CALL 1
> +
> union hv_ghcb {
> struct ghcb ghcb;
> + struct {
> + u64 hypercalldata[509];
> + u64 outputgpa;
> + union {
> + union {
> + struct {
> + u32 callcode : 16;
> + u32 isfast : 1;
> + u32 reserved1 : 14;
> + u32 isnested : 1;
> + u32 countofelements : 12;
> + u32 reserved2 : 4;
> + u32 repstartindex : 12;
> + u32 reserved3 : 4;
> + };
> + u64 asuint64;
> + } hypercallinput;
> + union {
> + struct {
> + u16 callstatus;
> + u16 reserved1;
> + u32 elementsprocessed : 12;
> + u32 reserved2 : 20;
> + };
> + u64 asunit64;
> + } hypercalloutput;
> + };
> + u64 reserved2;
> + } hypercall;
> } __packed __aligned(HV_HYP_PAGE_SIZE);
>
> +u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size)
> +{
> + union hv_ghcb *hv_ghcb;
> + void **ghcb_base;
> + unsigned long flags;
> +
> + if (!hv_ghcb_pg)
> + return -EFAULT;
> +
> + WARN_ON(in_nmi());
> +
> + local_irq_save(flags);
> + ghcb_base = (void **)this_cpu_ptr(hv_ghcb_pg);
> + hv_ghcb = (union hv_ghcb *)*ghcb_base;
> + if (!hv_ghcb) {
> + local_irq_restore(flags);
> + return -EFAULT;
> + }
> +
> + hv_ghcb->ghcb.protocol_version = GHCB_PROTOCOL_MAX;
> + hv_ghcb->ghcb.ghcb_usage = GHCB_USAGE_HYPERV_CALL;
> +
> + hv_ghcb->hypercall.outputgpa = (u64)output;
> + hv_ghcb->hypercall.hypercallinput.asuint64 = 0;
> + hv_ghcb->hypercall.hypercallinput.callcode = control;
> +
> + if (input_size)
> + memcpy(hv_ghcb->hypercall.hypercalldata, input, input_size);
> +
> + VMGEXIT();
> +
> + hv_ghcb->ghcb.ghcb_usage = 0xffffffff;
> + memset(hv_ghcb->ghcb.save.valid_bitmap, 0,
> + sizeof(hv_ghcb->ghcb.save.valid_bitmap));
> +
> + local_irq_restore(flags);
> +
> + return hv_ghcb->hypercall.hypercalloutput.callstatus;
The hypercall.hypercalloutput.callstatus value must be saved
in a local variable *before* the call to local_irq_restore(). Then
the local variable is the return value. Once local_irq_restore()
is called, the GHCB page could get reused.
> +}
> +
> void hv_ghcb_msr_write(u64 msr, u64 value)
> {
> union hv_ghcb *hv_ghcb;
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 5e479d54918c..6d315c1465e0 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -447,6 +447,10 @@ void vmbus_set_event(struct vmbus_channel *channel)
>
> ++channel->sig_events;
>
> - hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, channel->sig_event);
> + if (hv_isolation_type_snp())
> + hv_ghcb_hypercall(HVCALL_SIGNAL_EVENT, &channel->sig_event,
> + NULL, sizeof(u64));
Better to use "sizeof(channel->sig_event)" instead of explicitly coding
the type.
> + else
> + hv_do_fast_hypercall8(HVCALL_SIGNAL_EVENT, channel->sig_event);
> }
> EXPORT_SYMBOL_GPL(vmbus_set_event);
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 97b21256a9db..d4531c64d9d3 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -98,7 +98,13 @@ int hv_post_message(union hv_connection_id connection_id,
> aligned_msg->payload_size = payload_size;
> memcpy((void *)aligned_msg->payload, payload, payload_size);
>
> - status = hv_do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL);
> + if (hv_isolation_type_snp())
> + status = hv_ghcb_hypercall(HVCALL_POST_MESSAGE,
> + (void *)aligned_msg, NULL,
> + sizeof(struct hv_input_post_message));
As above, use "sizeof(*aligned_msg)".
> + else
> + status = hv_do_hypercall(HVCALL_POST_MESSAGE,
> + aligned_msg, NULL);
>
> /* Preemption must remain disabled until after the hypercall
> * so some other thread can't get scheduled onto this cpu and
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 1fc82d237161..7be173a99f27 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -289,3 +289,9 @@ void __weak hyperv_cleanup(void)
> {
> }
> EXPORT_SYMBOL_GPL(hyperv_cleanup);
> +
> +u64 __weak hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size)
> +{
> + return HV_STATUS_INVALID_PARAMETER;
> +}
> +EXPORT_SYMBOL_GPL(hv_ghcb_hypercall);
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 04a687d95eac..0da45807c36a 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -250,6 +250,7 @@ bool hv_is_hibernation_supported(void);
> enum hv_isolation_type hv_get_isolation_type(void);
> bool hv_is_isolation_supported(void);
> bool hv_isolation_type_snp(void);
> +u64 hv_ghcb_hypercall(u64 control, void *input, void *output, u32 input_size);
> void hyperv_cleanup(void);
> bool hv_query_ext_cap(u64 cap_query);
> #else /* CONFIG_HYPERV */
> --
> 2.25.1
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