Re: [Resend RFC PATCH V2 07/12] HV/Vmbus: Initialize VMbus ring buffer for Isolation VM

From: Konrad Rzeszutek Wilk
Date: Thu Apr 15 2021 - 16:25:17 EST

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In reply to: Tianyu Lan: "[Resend RFC PATCH V2 07/12] HV/Vmbus: Initialize VMbus ring buffer for Isolation VM"
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On Wed, Apr 14, 2021 at 10:49:40AM -0400, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
>
> VMbus ring buffer are shared with host and it's need to
> be accessed via extra address space of Isolation VM with
> SNP support. This patch is to map the ring buffer
> address in extra address space via ioremap(). HV host

Why do you need to use ioremap()? Why not just use vmap?

> visibility hvcall smears data in the ring buffer and
> so reset the ring buffer memory to zero after calling
> visibility hvcall.

So you are exposing these two:
EXPORT_SYMBOL_GPL(get_vm_area);
EXPORT_SYMBOL_GPL(ioremap_page_range);

But if you used vmap wouldn't you get the same thing for free?

>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
> drivers/hv/channel.c | 10 +++++
> drivers/hv/hyperv_vmbus.h | 2 +
> drivers/hv/ring_buffer.c | 83 +++++++++++++++++++++++++++++----------
> mm/ioremap.c | 1 +
> mm/vmalloc.c | 1 +
> 5 files changed, 76 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 407b74d72f3f..4a9fb7ad4c72 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -634,6 +634,16 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
> if (err)
> goto error_clean_ring;
>
> + err = hv_ringbuffer_post_init(&newchannel->outbound,
> + page, send_pages);
> + if (err)
> + goto error_free_gpadl;
> +
> + err = hv_ringbuffer_post_init(&newchannel->inbound,
> + &page[send_pages], recv_pages);
> + if (err)
> + goto error_free_gpadl;
> +
> /* Create and init the channel open message */
> open_info = kzalloc(sizeof(*open_info) +
> sizeof(struct vmbus_channel_open_channel),
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 0778add21a9c..d78a04ad5490 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -172,6 +172,8 @@ extern int hv_synic_cleanup(unsigned int cpu);
> /* Interface */
>
> void hv_ringbuffer_pre_init(struct vmbus_channel *channel);
> +int hv_ringbuffer_post_init(struct hv_ring_buffer_info *ring_info,
> + struct page *pages, u32 page_cnt);
>
> int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
> struct page *pages, u32 pagecnt);
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index 35833d4d1a1d..c8b0f7b45158 100644
> --- a/drivers/hv/ring_buffer.c
> +++ b/drivers/hv/ring_buffer.c
> @@ -17,6 +17,8 @@
> #include <linux/vmalloc.h>
> #include <linux/slab.h>
> #include <linux/prefetch.h>
> +#include <linux/io.h>
> +#include <asm/mshyperv.h>
>
> #include "hyperv_vmbus.h"
>
> @@ -188,6 +190,44 @@ void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
> mutex_init(&channel->outbound.ring_buffer_mutex);
> }
>
> +int hv_ringbuffer_post_init(struct hv_ring_buffer_info *ring_info,
> + struct page *pages, u32 page_cnt)
> +{
> + struct vm_struct *area;
> + u64 physic_addr = page_to_pfn(pages) << PAGE_SHIFT;
> + unsigned long vaddr;
> + int err = 0;
> +
> + if (!hv_isolation_type_snp())
> + return 0;
> +
> + physic_addr += ms_hyperv.shared_gpa_boundary;
> + area = get_vm_area((2 * page_cnt - 1) * PAGE_SIZE, VM_IOREMAP);
> + if (!area || !area->addr)
> + return -EFAULT;
> +
> + vaddr = (unsigned long)area->addr;
> + err = ioremap_page_range(vaddr, vaddr + page_cnt * PAGE_SIZE,
> + physic_addr, PAGE_KERNEL_IO);
> + err |= ioremap_page_range(vaddr + page_cnt * PAGE_SIZE,
> + vaddr + (2 * page_cnt - 1) * PAGE_SIZE,
> + physic_addr + PAGE_SIZE, PAGE_KERNEL_IO);
> + if (err) {
> + vunmap((void *)vaddr);
> + return -EFAULT;
> + }
> +
> + /* Clean memory after setting host visibility. */
> + memset((void *)vaddr, 0x00, page_cnt * PAGE_SIZE);
> +
> + ring_info->ring_buffer = (struct hv_ring_buffer *)vaddr;
> + ring_info->ring_buffer->read_index = 0;
> + ring_info->ring_buffer->write_index = 0;
> + ring_info->ring_buffer->feature_bits.value = 1;
> +
> + return 0;
> +}
> +
> /* Initialize the ring buffer. */
> int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
> struct page *pages, u32 page_cnt)
> @@ -197,33 +237,34 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
>
> BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
>
> - /*
> - * First page holds struct hv_ring_buffer, do wraparound mapping for
> - * the rest.
> - */
> - pages_wraparound = kcalloc(page_cnt * 2 - 1, sizeof(struct page *),
> - GFP_KERNEL);
> - if (!pages_wraparound)
> - return -ENOMEM;
> -
> - pages_wraparound[0] = pages;
> - for (i = 0; i < 2 * (page_cnt - 1); i++)
> - pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];
> + if (!hv_isolation_type_snp()) {
> + /*
> + * First page holds struct hv_ring_buffer, do wraparound mapping for
> + * the rest.
> + */
> + pages_wraparound = kcalloc(page_cnt * 2 - 1, sizeof(struct page *),
> + GFP_KERNEL);
> + if (!pages_wraparound)
> + return -ENOMEM;
>
> - ring_info->ring_buffer = (struct hv_ring_buffer *)
> - vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);
> + pages_wraparound[0] = pages;
> + for (i = 0; i < 2 * (page_cnt - 1); i++)
> + pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];
>
> - kfree(pages_wraparound);
> + ring_info->ring_buffer = (struct hv_ring_buffer *)
> + vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);
>
> + kfree(pages_wraparound);
>
> - if (!ring_info->ring_buffer)
> - return -ENOMEM;
> + if (!ring_info->ring_buffer)
> + return -ENOMEM;
>
> - ring_info->ring_buffer->read_index =
> - ring_info->ring_buffer->write_index = 0;
> + ring_info->ring_buffer->read_index =
> + ring_info->ring_buffer->write_index = 0;
>
> - /* Set the feature bit for enabling flow control. */
> - ring_info->ring_buffer->feature_bits.value = 1;
> + /* Set the feature bit for enabling flow control. */
> + ring_info->ring_buffer->feature_bits.value = 1;
> + }
>
> ring_info->ring_size = page_cnt << PAGE_SHIFT;
> ring_info->ring_size_div10_reciprocal =
> diff --git a/mm/ioremap.c b/mm/ioremap.c
> index 5fa1ab41d152..d63c4ba067f9 100644
> --- a/mm/ioremap.c
> +++ b/mm/ioremap.c
> @@ -248,6 +248,7 @@ int ioremap_page_range(unsigned long addr,
>
> return err;
> }
> +EXPORT_SYMBOL_GPL(ioremap_page_range);
>
> #ifdef CONFIG_GENERIC_IOREMAP
> void __iomem *ioremap_prot(phys_addr_t addr, size_t size, unsigned long prot)
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index e6f352bf0498..19724a8ebcb7 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2131,6 +2131,7 @@ struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
> NUMA_NO_NODE, GFP_KERNEL,
> __builtin_return_address(0));
> }
> +EXPORT_SYMBOL_GPL(get_vm_area);
>
> struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
> const void *caller)
> --
> 2.25.1
>

Next message: Wei Xu: "Re: [PATCH 02/10] mm/numa: automatically generate node migration order"
Previous message: Mathieu Poirier: "[PATCH 1/1] coresight: etm-perf: Fix define build issue when built as module"
In reply to: Tianyu Lan: "[Resend RFC PATCH V2 07/12] HV/Vmbus: Initialize VMbus ring buffer for Isolation VM"
Next in thread: Tianyu Lan: "[Resend RFC PATCH V2 08/12] UIO/Hyper-V: Not load UIO HV driver in the isolation VM."
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