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Message-ID: <MWHPR21MB1593CF062ACBE0707D0F46AFD7CE9@MWHPR21MB1593.namprd21.prod.outlook.com>
Date: Thu, 2 Sep 2021 00:21:24 +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>,
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"bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
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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>,
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vkuznets <vkuznets@...hat.com>,
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"dave.hansen@...el.com" <dave.hansen@...el.com>
Subject: RE: [PATCH V4 07/13] hyperv/Vmbus: Add SNP support for VMbus channel
initiate message
From: Tianyu Lan <ltykernel@...il.com> Sent: Friday, August 27, 2021 10:21 AM
>
Subject line tag should be "Drivers: hv: vmbus:"
> The monitor pages in the CHANNELMSG_INITIATE_CONTACT msg are shared
> with host in Isolation VM and so it's necessary to use hvcall to set
> them visible to host. In Isolation VM with AMD SEV SNP, the access
> address should be in the extra space which is above shared gpa
> boundary. So remap these pages into the extra address(pa +
> shared_gpa_boundary).
>
> Introduce monitor_pages_original[] in the struct vmbus_connection
> to store monitor page virtual address returned by hv_alloc_hyperv_
> zeroed_page() and free monitor page via monitor_pages_original in
> the vmbus_disconnect(). The monitor_pages[] is to used to access
> monitor page and it is initialized to be equal with monitor_pages_
> original. The monitor_pages[] will be overridden in the isolation VM
> with va of extra address.
>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> ---
> Change since v3:
> * Rename monitor_pages_va with monitor_pages_original
> * free monitor page via monitor_pages_original and
> monitor_pages is used to access monitor page.
>
> Change since v1:
> * Not remap monitor pages in the non-SNP isolation VM.
> ---
> drivers/hv/connection.c | 75 ++++++++++++++++++++++++++++++++++++---
> drivers/hv/hyperv_vmbus.h | 1 +
> 2 files changed, 72 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 6d315c1465e0..9a48d8115c87 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -19,6 +19,7 @@
> #include <linux/vmalloc.h>
> #include <linux/hyperv.h>
> #include <linux/export.h>
> +#include <linux/io.h>
> #include <asm/mshyperv.h>
>
> #include "hyperv_vmbus.h"
> @@ -104,6 +105,12 @@ int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
>
> msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages[0]);
> msg->monitor_page2 = virt_to_phys(vmbus_connection.monitor_pages[1]);
> +
> + if (hv_isolation_type_snp()) {
> + msg->monitor_page1 += ms_hyperv.shared_gpa_boundary;
> + msg->monitor_page2 += ms_hyperv.shared_gpa_boundary;
> + }
> +
> msg->target_vcpu = hv_cpu_number_to_vp_number(VMBUS_CONNECT_CPU);
>
> /*
> @@ -148,6 +155,35 @@ int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
> return -ECONNREFUSED;
> }
>
> +
> + if (hv_is_isolation_supported()) {
> + if (hv_isolation_type_snp()) {
> + vmbus_connection.monitor_pages[0]
> + = memremap(msg->monitor_page1, HV_HYP_PAGE_SIZE,
> + MEMREMAP_WB);
> + if (!vmbus_connection.monitor_pages[0])
> + return -ENOMEM;
> +
> + vmbus_connection.monitor_pages[1]
> + = memremap(msg->monitor_page2, HV_HYP_PAGE_SIZE,
> + MEMREMAP_WB);
> + if (!vmbus_connection.monitor_pages[1]) {
> + memunmap(vmbus_connection.monitor_pages[0]);
> + return -ENOMEM;
> + }
> + }
> +
> + /*
> + * Set memory host visibility hvcall smears memory
> + * and so zero monitor pages here.
> + */
> + memset(vmbus_connection.monitor_pages[0], 0x00,
> + HV_HYP_PAGE_SIZE);
> + memset(vmbus_connection.monitor_pages[1], 0x00,
> + HV_HYP_PAGE_SIZE);
> +
> + }
I still find it somewhat confusing to have the handling of the
shared_gpa_boundary and memory mapping in the function for
negotiating the VMbus version. I think the code works as written,
but it would seem cleaner and easier to understand to precompute
the physical addresses and do all the mapping and memory zero'ing
in a single place in vmbus_connect(). Then the negotiate version
function can focus on doing only the version negotiation.
> +
> return ret;
> }
>
> @@ -159,6 +195,7 @@ int vmbus_connect(void)
> struct vmbus_channel_msginfo *msginfo = NULL;
> int i, ret = 0;
> __u32 version;
> + u64 pfn[2];
>
> /* Initialize the vmbus connection */
> vmbus_connection.conn_state = CONNECTING;
> @@ -216,6 +253,21 @@ int vmbus_connect(void)
> goto cleanup;
> }
>
> + vmbus_connection.monitor_pages_original[0]
> + = vmbus_connection.monitor_pages[0];
> + vmbus_connection.monitor_pages_original[1]
> + = vmbus_connection.monitor_pages[1];
> +
> + if (hv_is_isolation_supported()) {
> + pfn[0] = virt_to_hvpfn(vmbus_connection.monitor_pages[0]);
> + pfn[1] = virt_to_hvpfn(vmbus_connection.monitor_pages[1]);
> + if (hv_mark_gpa_visibility(2, pfn,
> + VMBUS_PAGE_VISIBLE_READ_WRITE)) {
In Patch 4 of this series, host visibility for the specified buffer is done
by calling set_memory_decrypted()/set_memory_encrypted(). Could
the same be done here? The code would be more consistent overall
with better encapsulation. hv_mark_gpa_visibility() would not need to
be exported or need an ARM64 stub.
set_memory_decrypted()/encrypted() seem to be the primary functions
that should be used for this purpose, and they have already have the
appropriate stubs for architectures that don't support memory encryption.
> + ret = -EFAULT;
> + goto cleanup;
> + }
> + }
> +
> msginfo = kzalloc(sizeof(*msginfo) +
> sizeof(struct vmbus_channel_initiate_contact),
> GFP_KERNEL);
> @@ -284,6 +336,8 @@ int vmbus_connect(void)
>
> void vmbus_disconnect(void)
> {
> + u64 pfn[2];
> +
> /*
> * First send the unload request to the host.
> */
> @@ -303,10 +357,23 @@ void vmbus_disconnect(void)
> vmbus_connection.int_page = NULL;
> }
>
> - hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[0]);
> - hv_free_hyperv_page((unsigned long)vmbus_connection.monitor_pages[1]);
> - vmbus_connection.monitor_pages[0] = NULL;
> - vmbus_connection.monitor_pages[1] = NULL;
> + if (hv_is_isolation_supported()) {
> + memunmap(vmbus_connection.monitor_pages[0]);
> + memunmap(vmbus_connection.monitor_pages[1]);
> +
> + pfn[0] = virt_to_hvpfn(vmbus_connection.monitor_pages[0]);
> + pfn[1] = virt_to_hvpfn(vmbus_connection.monitor_pages[1]);
> + hv_mark_gpa_visibility(2, pfn, VMBUS_PAGE_NOT_VISIBLE);
Same comment about using set_memory_encrypted() instead.
> + }
> +
> + hv_free_hyperv_page((unsigned long)
> + vmbus_connection.monitor_pages_original[0]);
> + hv_free_hyperv_page((unsigned long)
> + vmbus_connection.monitor_pages_original[1]);
> + vmbus_connection.monitor_pages_original[0] =
> + vmbus_connection.monitor_pages[0] = NULL;
> + vmbus_connection.monitor_pages_original[1] =
> + vmbus_connection.monitor_pages[1] = NULL;
> }
>
> /*
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 42f3d9d123a1..7cb11ef694da 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -240,6 +240,7 @@ struct vmbus_connection {
> * is child->parent notification
> */
> struct hv_monitor_page *monitor_pages[2];
> + void *monitor_pages_original[2];
> struct list_head chn_msg_list;
> spinlock_t channelmsg_lock;
>
> --
> 2.25.1
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