[PATCH v3 0/5] hv: Remove dependencies on guest page size

[PATCH v3 0/5] hv: Remove dependencies on guest page size

[Maya Nakamura]

The Linux guest page size and hypervisor page size concepts are
different, even though they happen to be the same value on x86. Hyper-V
code mixes up the two, so this patchset begins to address that by
creating and using a set of Hyper-V specific page definitions.

A major benefit of those new definitions is that they support non-x86
architectures, such as ARM64, that use different page sizes. On ARM64,
the guest page size may not be 4096, and Hyper-V always runs with a
page size of 4096.

In this patchset, the first two patches lay the foundation for the
others, creating definitions and preparing for allocation of memory with
the size and alignment that Hyper-V expects as a page. Patch 3 applies
the page size definition where the guest VM and Hyper-V communicate, and
where the code intends to use the Hyper-V page size. The last two
patches set the ring buffer size to a fixed value, removing the
dependency on the guest page size.

This is the initial set of changes to the Hyper-V code, and future
patches will make additional changes using the same foundation, for
example, replace __vmalloc() and related functions when Hyper-V pages
are intended.

Changes in v3:
- [PATCH v2 2/5] Simplify expression for BUILD_BUG_ON().
- Add Link and Reviewed-by tags.

Change in v2:
- [PATCH 2/5] Replace with a new patch.

Maya Nakamura (5):
  x86: hv: hyperv-tlfs.h: Create and use Hyper-V page definitions
  x86: hv: hv_init.c: Add functions to allocate/deallocate page for
    Hyper-V
  hv: vmbus: Replace page definition with Hyper-V specific one
  HID: hv: Remove dependencies on PAGE_SIZE for ring buffer
  Input: hv: Remove dependencies on PAGE_SIZE for ring buffer

 arch/x86/hyperv/hv_init.c             | 14 ++++++++++++++
 arch/x86/include/asm/hyperv-tlfs.h    | 12 +++++++++++-
 drivers/hid/hid-hyperv.c              |  4 ++--
 drivers/hv/hyperv_vmbus.h             |  8 ++++----
 drivers/input/serio/hyperv-keyboard.c |  4 ++--
 5 files changed, 33 insertions(+), 9 deletions(-)

-- 
2.17.1

[PATCH v3 1/5] x86: hv: hyperv-tlfs.h: Create and use Hyper-V page definitions

[Maya Nakamura]

Define HV_HYP_PAGE_SHIFT, HV_HYP_PAGE_SIZE, and HV_HYP_PAGE_MASK because
the Linux guest page size and hypervisor page size concepts are
different, even though they happen to be the same value on x86.

Also, replace PAGE_SIZE with HV_HYP_PAGE_SIZE.

Signed-off-by: Maya Nakamura <m.maya.nakamura@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/include/asm/hyperv-tlfs.h | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index af78cd72b8f3..4097edf552b3 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -12,6 +12,16 @@
 #include <linux/types.h>
 #include <asm/page.h>
 
+/*
+ * While not explicitly listed in the TLFS, Hyper-V always runs with a page size
+ * of 4096. These definitions are used when communicating with Hyper-V using
+ * guest physical pages and guest physical page addresses, since the guest page
+ * size may not be 4096 on all architectures.
+ */
+#define HV_HYP_PAGE_SHIFT	12
+#define HV_HYP_PAGE_SIZE	BIT(HV_HYP_PAGE_SHIFT)
+#define HV_HYP_PAGE_MASK	(~(HV_HYP_PAGE_SIZE - 1))
+
 /*
  * The below CPUID leaves are present if VersionAndFeatures.HypervisorPresent
  * is set by CPUID(HvCpuIdFunctionVersionAndFeatures).
@@ -847,7 +857,7 @@ union hv_gpa_page_range {
  * count is equal with how many entries of union hv_gpa_page_range can
  * be populated into the input parameter page.
  */
-#define HV_MAX_FLUSH_REP_COUNT ((PAGE_SIZE - 2 * sizeof(u64)) /	\
+#define HV_MAX_FLUSH_REP_COUNT ((HV_HYP_PAGE_SIZE - 2 * sizeof(u64)) / \
 				sizeof(union hv_gpa_page_range))
 
 struct hv_guest_mapping_flush_list {
-- 
2.17.1

[PATCH v3 2/5] x86: hv: hv_init.c: Add functions to allocate/deallocate page for Hyper-V

[Maya Nakamura]

Introduce two new functions, hv_alloc_hyperv_page() and
hv_free_hyperv_page(), to allocate/deallocate memory with the size and
alignment that Hyper-V expects as a page. Although currently they are
not used, they are ready to be used to allocate/deallocate memory on x86
when their ARM64 counterparts are implemented, keeping symmetry between
architectures with potentially different guest page sizes.

Link: https://lore.kernel.org/lkml/87muindr9c.fsf@vitty.brq.redhat.com/
Signed-off-by: Maya Nakamura <m.maya.nakamura@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/hyperv/hv_init.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 0e033ef11a9f..e8960a83add7 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -37,6 +37,20 @@ EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
 u32 hv_max_vp_index;
 EXPORT_SYMBOL_GPL(hv_max_vp_index);
 
+void *hv_alloc_hyperv_page(void)
+{
+	BUILD_BUG_ON(PAGE_SIZE != HV_HYP_PAGE_SIZE);
+
+	return (void *)__get_free_page(GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
+
+void hv_free_hyperv_page(unsigned long addr)
+{
+	free_page(addr);
+}
+EXPORT_SYMBOL_GPL(hv_free_hyperv_page);
+
 static int hv_cpu_init(unsigned int cpu)
 {
 	u64 msr_vp_index;
-- 
2.17.1

[PATCH v3 3/5] hv: vmbus: Replace page definition with Hyper-V specific one

[Maya Nakamura]

Replace PAGE_SIZE with HV_HYP_PAGE_SIZE because the guest page size may
not be 4096 on all architectures and Hyper-V always runs with a page
size of 4096.

Signed-off-by: Maya Nakamura <m.maya.nakamura@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hv/hyperv_vmbus.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 362e70e9d145..019469c3cbca 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -192,11 +192,11 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
 		       u64 *requestid, bool raw);
 
 /*
- * Maximum channels is determined by the size of the interrupt page
- * which is PAGE_SIZE. 1/2 of PAGE_SIZE is for send endpoint interrupt
- * and the other is receive endpoint interrupt
+ * Maximum channels, 16348, is determined by the size of the interrupt page,
+ * which is HV_HYP_PAGE_SIZE. 1/2 of HV_HYP_PAGE_SIZE is to send endpoint
+ * interrupt, and the other is to receive endpoint interrupt.
  */
-#define MAX_NUM_CHANNELS	((PAGE_SIZE >> 1) << 3)	/* 16348 channels */
+#define MAX_NUM_CHANNELS	((HV_HYP_PAGE_SIZE >> 1) << 3)
 
 /* The value here must be in multiple of 32 */
 /* TODO: Need to make this configurable */
-- 
2.17.1

[PATCH v3 4/5] HID: hv: Remove dependencies on PAGE_SIZE for ring buffer

[Maya Nakamura]

Define the ring buffer size as a constant expression because it should
not depend on the guest page size.

Signed-off-by: Maya Nakamura <m.maya.nakamura@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
 drivers/hid/hid-hyperv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-hyperv.c b/drivers/hid/hid-hyperv.c
index 7795831d37c2..cc5b09b87ab0 100644
--- a/drivers/hid/hid-hyperv.c
+++ b/drivers/hid/hid-hyperv.c
@@ -104,8 +104,8 @@ struct synthhid_input_report {
 
 #pragma pack(pop)
 
-#define INPUTVSC_SEND_RING_BUFFER_SIZE		(10*PAGE_SIZE)
-#define INPUTVSC_RECV_RING_BUFFER_SIZE		(10*PAGE_SIZE)
+#define INPUTVSC_SEND_RING_BUFFER_SIZE		(40 * 1024)
+#define INPUTVSC_RECV_RING_BUFFER_SIZE		(40 * 1024)
 
 
 enum pipe_prot_msg_type {
-- 
2.17.1

[PATCH v3 5/5] Input: hv: Remove dependencies on PAGE_SIZE for ring buffer

[Maya Nakamura]

Define the ring buffer size as a constant expression because it should
not depend on the guest page size.

Signed-off-by: Maya Nakamura <m.maya.nakamura@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
 drivers/input/serio/hyperv-keyboard.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/serio/hyperv-keyboard.c b/drivers/input/serio/hyperv-keyboard.c
index 8e457e50f837..88ae7c2ac3c8 100644
--- a/drivers/input/serio/hyperv-keyboard.c
+++ b/drivers/input/serio/hyperv-keyboard.c
@@ -75,8 +75,8 @@ struct synth_kbd_keystroke {
 
 #define HK_MAXIMUM_MESSAGE_SIZE 256
 
-#define KBD_VSC_SEND_RING_BUFFER_SIZE		(10 * PAGE_SIZE)
-#define KBD_VSC_RECV_RING_BUFFER_SIZE		(10 * PAGE_SIZE)
+#define KBD_VSC_SEND_RING_BUFFER_SIZE		(40 * 1024)
+#define KBD_VSC_RECV_RING_BUFFER_SIZE		(40 * 1024)
 
 #define XTKBD_EMUL0     0xe0
 #define XTKBD_EMUL1     0xe1
-- 
2.17.1

Re: [PATCH v3 2/5] x86: hv: hv_init.c: Add functions to allocate/deallocate page for Hyper-V

[Thomas Gleixner]

Maya,

On Tue, 18 Jun 2019, Maya Nakamura wrote:

> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 0e033ef11a9f..e8960a83add7 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -37,6 +37,20 @@ EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
>  u32 hv_max_vp_index;
>  EXPORT_SYMBOL_GPL(hv_max_vp_index);
>  
> +void *hv_alloc_hyperv_page(void)
> +{
> +	BUILD_BUG_ON(PAGE_SIZE != HV_HYP_PAGE_SIZE);
> +
> +	return (void *)__get_free_page(GFP_KERNEL);
> +}
> +EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
> +
> +void hv_free_hyperv_page(unsigned long addr)
> +{
> +	free_page(addr);
> +}
> +EXPORT_SYMBOL_GPL(hv_free_hyperv_page);

These functions need to be declared in a header file.

Thanks,

	tglx

Re: [PATCH v3 2/5] x86: hv: hv_init.c: Add functions to allocate/deallocate page for Hyper-V

[Maya Nakamura]

On Thu, Jun 27, 2019 at 11:38:14PM +0200, Thomas Gleixner wrote:
> Maya,
> 
> On Tue, 18 Jun 2019, Maya Nakamura wrote:
> 
> > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> > index 0e033ef11a9f..e8960a83add7 100644
> > --- a/arch/x86/hyperv/hv_init.c
> > +++ b/arch/x86/hyperv/hv_init.c
> > @@ -37,6 +37,20 @@ EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
> >  u32 hv_max_vp_index;
> >  EXPORT_SYMBOL_GPL(hv_max_vp_index);
> >  
> > +void *hv_alloc_hyperv_page(void)
> > +{
> > +	BUILD_BUG_ON(PAGE_SIZE != HV_HYP_PAGE_SIZE);
> > +
> > +	return (void *)__get_free_page(GFP_KERNEL);
> > +}
> > +EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
> > +
> > +void hv_free_hyperv_page(unsigned long addr)
> > +{
> > +	free_page(addr);
> > +}
> > +EXPORT_SYMBOL_GPL(hv_free_hyperv_page);
> 
> These functions need to be declared in a header file.
> 
> Thanks,
> 
> 	tglx
> 
Thank you for pointing that out, Thomas. I will resubmit my patch set to
include a header file with the function prototypes.