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

[Michael Kelley <mikelley@xxxxxxxxxxxxx>]

From: Tianyu Lan <ltykernel@xxxxxxxxx> 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@xxxxxxxxxxxxx>
> ---
> 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