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Message-ID: <CAMvTesBiSOsxywS+JxAB+oAh9i1UEbngAXeZJdi7SWqm9pAd9A@mail.gmail.com>
Date: Fri, 25 Jul 2025 22:40:29 +0800
From: Tianyu Lan <ltykernel@...il.com>
To: Roman Kisel <romank@...ux.microsoft.com>
Cc: alok.a.tiwari@...cle.com, arnd@...db.de, bp@...en8.de, corbet@....net,
dave.hansen@...ux.intel.com, decui@...rosoft.com, haiyangz@...rosoft.com,
hpa@...or.com, kys@...rosoft.com, mhklinux@...look.com, mingo@...hat.com,
rdunlap@...radead.org, tglx@...utronix.de, Tianyu.Lan@...rosoft.com,
wei.liu@...nel.org, linux-arch@...r.kernel.org, linux-coco@...ts.linux.dev,
linux-doc@...r.kernel.org, linux-hyperv@...r.kernel.org,
linux-kernel@...r.kernel.org, x86@...nel.org, apais@...rosoft.com,
benhill@...rosoft.com, bperkins@...rosoft.com, sunilmut@...rosoft.com
Subject: Re: [PATCH hyperv-next v4 12/16] Drivers: hv: Allocate encrypted
buffers when requested
On Tue, Jul 15, 2025 at 6:28 AM Roman Kisel <romank@...ux.microsoft.com> wrote:
>
> Confidential VMBus is built around using buffers not shared with
> the host.
>
> Support allocating encrypted buffers when requested.
>
> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
> ---
Reviewed-by: Tianyu Lan <tiala@...rosoft.com>
> drivers/hv/channel.c | 49 +++++++++++++++++++++++----------------
> drivers/hv/hyperv_vmbus.h | 3 ++-
> drivers/hv/ring_buffer.c | 5 ++--
> 3 files changed, 34 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 35f26fa1ffe7..051eeba800f2 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -443,20 +443,23 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> return ret;
> }
>
> - /*
> - * Set the "decrypted" flag to true for the set_memory_decrypted()
> - * success case. In the failure case, the encryption state of the
> - * memory is unknown. Leave "decrypted" as true to ensure the
> - * memory will be leaked instead of going back on the free list.
> - */
> - gpadl->decrypted = true;
> - ret = set_memory_decrypted((unsigned long)kbuffer,
> - PFN_UP(size));
> - if (ret) {
> - dev_warn(&channel->device_obj->device,
> - "Failed to set host visibility for new GPADL %d.\n",
> - ret);
> - return ret;
> + gpadl->decrypted = !((channel->co_external_memory && type == HV_GPADL_BUFFER) ||
> + (channel->co_ring_buffer && type == HV_GPADL_RING));
> + if (gpadl->decrypted) {
> + /*
> + * The "decrypted" flag being true assumes that set_memory_decrypted() succeeds.
> + * But if it fails, the encryption state of the memory is unknown. In that case,
> + * leave "decrypted" as true to ensure the memory is leaked instead of going back
> + * on the free list.
> + */
> + ret = set_memory_decrypted((unsigned long)kbuffer,
> + PFN_UP(size));
> + if (ret) {
> + dev_warn(&channel->device_obj->device,
> + "Failed to set host visibility for new GPADL %d.\n",
> + ret);
> + return ret;
> + }
> }
>
> init_completion(&msginfo->waitevent);
> @@ -544,8 +547,10 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
> * left as true so the memory is leaked instead of being
> * put back on the free list.
> */
> - if (!set_memory_encrypted((unsigned long)kbuffer, PFN_UP(size)))
> - gpadl->decrypted = false;
> + if (gpadl->decrypted) {
> + if (!set_memory_encrypted((unsigned long)kbuffer, PFN_UP(size)))
> + gpadl->decrypted = false;
> + }
> }
>
> return ret;
> @@ -676,12 +681,13 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> goto error_clean_ring;
>
> err = hv_ringbuffer_init(&newchannel->outbound,
> - page, send_pages, 0);
> + page, send_pages, 0, newchannel->co_ring_buffer);
> if (err)
> goto error_free_gpadl;
>
> err = hv_ringbuffer_init(&newchannel->inbound, &page[send_pages],
> - recv_pages, newchannel->max_pkt_size);
> + recv_pages, newchannel->max_pkt_size,
> + newchannel->co_ring_buffer);
> if (err)
> goto error_free_gpadl;
>
> @@ -862,8 +868,11 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, struct vmbus_gpadl *gpad
>
> kfree(info);
>
> - ret = set_memory_encrypted((unsigned long)gpadl->buffer,
> - PFN_UP(gpadl->size));
> + if (gpadl->decrypted)
> + ret = set_memory_encrypted((unsigned long)gpadl->buffer,
> + PFN_UP(gpadl->size));
> + else
> + ret = 0;
> if (ret)
> pr_warn("Fail to set mem host visibility in GPADL teardown %d.\n", ret);
>
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 2873703d08a9..beae68a70939 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -200,7 +200,8 @@ extern int hv_synic_cleanup(unsigned int cpu);
> void hv_ringbuffer_pre_init(struct vmbus_channel *channel);
>
> int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
> - struct page *pages, u32 pagecnt, u32 max_pkt_size);
> + struct page *pages, u32 pagecnt, u32 max_pkt_size,
> + bool confidential);
>
> void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info);
>
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index 3c9b02471760..05c2cd42fc75 100644
> --- a/drivers/hv/ring_buffer.c
> +++ b/drivers/hv/ring_buffer.c
> @@ -183,7 +183,8 @@ void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
>
> /* Initialize the ring buffer. */
> int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
> - struct page *pages, u32 page_cnt, u32 max_pkt_size)
> + struct page *pages, u32 page_cnt, u32 max_pkt_size,
> + bool confidential)
> {
> struct page **pages_wraparound;
> int i;
> @@ -207,7 +208,7 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
>
> ring_info->ring_buffer = (struct hv_ring_buffer *)
> vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP,
> - pgprot_decrypted(PAGE_KERNEL));
> + confidential ? PAGE_KERNEL : pgprot_decrypted(PAGE_KERNEL));
>
> kfree(pages_wraparound);
> if (!ring_info->ring_buffer)
> --
> 2.43.0
>
>
--
Thanks
Tianyu Lan
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