RE: [PATCH V5 07/12] Drivers: hv: vmbus: Add SNP support for VMbus channel initiate message

Michael Kelley
2021-09-15T15:42:04Z

From: Tianyu Lan <ltykernel@gmail.com> Sent: Tuesday, September 14, 2021 6:39 AM
>
> 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. Introduce monitor_pages_pa[] to store
> monitor pages' physical address and use it to populate pa in the
> initiate msg.
>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> ---
> Change since v4:
> * Introduce monitor_pages_pa[] to store monitor pages' physical
> address and use it to populate pa in the initiate msg.
> * Move code of mapping moniter pages in extra address into
> vmbus_connect().
>
> 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 | 90 ++++++++++++++++++++++++++++++++++++---
> drivers/hv/hyperv_vmbus.h | 2 +
> 2 files changed, 86 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 8820ae68f20f..edd8f7dd169f 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -19,6 +19,8 @@
> #include <linux/vmalloc.h>
> #include <linux/hyperv.h>
> #include <linux/export.h>
> +#include <linux/io.h>
> +#include <linux/set_memory.h>
> #include <asm/mshyperv.h>
>
> #include "hyperv_vmbus.h"
> @@ -102,8 +104,9 @@ int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo, u32 version)
> vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID;
> }
>
> - msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages[0]);
> - msg->monitor_page2 = virt_to_phys(vmbus_connection.monitor_pages[1]);
> + msg->monitor_page1 = vmbus_connection.monitor_pages_pa[0];
> + msg->monitor_page2 = vmbus_connection.monitor_pages_pa[1];
> +
> msg->target_vcpu = hv_cpu_number_to_vp_number(VMBUS_CONNECT_CPU);
>
> /*
> @@ -216,6 +219,65 @@ 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];
> + vmbus_connection.monitor_pages_pa[0]
> + = virt_to_phys(vmbus_connection.monitor_pages[0]);
> + vmbus_connection.monitor_pages_pa[1]
> + = virt_to_phys(vmbus_connection.monitor_pages[1]);
> +
> + if (hv_is_isolation_supported()) {
> + vmbus_connection.monitor_pages_pa[0] +=
> + ms_hyperv.shared_gpa_boundary;
> + vmbus_connection.monitor_pages_pa[1] +=
> + ms_hyperv.shared_gpa_boundary;
> +
> + ret = set_memory_decrypted((unsigned long)
> + vmbus_connection.monitor_pages[0],
> + 1);
> + ret |= set_memory_decrypted((unsigned long)
> + vmbus_connection.monitor_pages[1],
> + 1);
> + if (ret)
> + goto cleanup;
> +
> + /*
> + * Isolation VM with AMD SNP needs to access monitor page via
> + * address space above shared gpa boundary.
> + */
> + if (hv_isolation_type_snp()) {
> + vmbus_connection.monitor_pages[0]
> + = memremap(vmbus_connection.monitor_pages_pa[0],
> + HV_HYP_PAGE_SIZE,
> + MEMREMAP_WB);
> + if (!vmbus_connection.monitor_pages[0]) {
> + ret = -ENOMEM;
> + goto cleanup;
> + }
> +
> + vmbus_connection.monitor_pages[1]
> + = memremap(vmbus_connection.monitor_pages_pa[1],
> + HV_HYP_PAGE_SIZE,
> + MEMREMAP_WB);
> + if (!vmbus_connection.monitor_pages[1]) {
> + ret = -ENOMEM;
> + goto cleanup;
> + }
> + }
> +
> + /*
> + * 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);
> +
> + }
> +

This all looks good. To me, this is a lot clearer to have all the mapping
and encryption/decryption handled in one place.

> msginfo = kzalloc(sizeof(*msginfo) +
> sizeof(struct vmbus_channel_initiate_contact),
> GFP_KERNEL);
> @@ -303,10 +365,26 @@ 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]);
> +
> + set_memory_encrypted((unsigned long)
> + vmbus_connection.monitor_pages_original[0],
> + 1);
> + set_memory_encrypted((unsigned long)
> + vmbus_connection.monitor_pages_original[1],
> + 1);
> + }
> +
> + 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..560cba916d1d 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -240,6 +240,8 @@ struct vmbus_connection {
> * is child->parent notification
> */
> struct hv_monitor_page *monitor_pages[2];
> + void *monitor_pages_original[2];
> + unsigned long monitor_pages_pa[2];

The type of this field really should be phys_addr_t. In addition to
just making semantic sense, then it will match the return type from
virt_to_phys() and the input arg to memremap() since resource_size_t
is typedef'ed as phys_addr_t.

> struct list_head chn_msg_list;
> spinlock_t channelmsg_lock;
>
> --
> 2.25.1