Commit a3b74243 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Ingo Molnar
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x86/hyperv: Clear vCPU banks between calls to avoid flushing unneeded vCPUs 



hv_flush_pcpu_ex structures are not cleared between calls for performance
reasons (they're variable size up to PAGE_SIZE each) but we must clear
hv_vp_set.bank_contents part of it to avoid flushing unneeded vCPUs. The
rest of the structure is formed correctly.

To do the clearing in an efficient way stash the maximum possible vCPU
number (this may differ from Linux CPU id).

Reported-by: default avatarJork Loeser <Jork.Loeser@microsoft.com>
Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Cc: Dexuan Cui <decui@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: devel@linuxdriverproject.org
Link: http://lkml.kernel.org/r/20171006154854.18092-1-vkuznets@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d4a2d031

arch/x86/hyperv/hv_init.c

+5 −0
Original line number Diff line number Diff line
@@ -85,6 +85,8 @@ EXPORT_SYMBOL_GPL(hyperv_cs); 
u32 *hv_vp_index;

EXPORT_SYMBOL_GPL(hv_vp_index);



u32 hv_max_vp_index;



static int hv_cpu_init(unsigned int cpu)

{

	u64 msr_vp_index;
@@ -93,6 +95,9 @@ static int hv_cpu_init(unsigned int cpu) 


	hv_vp_index[smp_processor_id()] = msr_vp_index;



	if (msr_vp_index > hv_max_vp_index)

		hv_max_vp_index = msr_vp_index;



	return 0;

}

arch/x86/hyperv/mmu.c

+12 −5
Original line number Diff line number Diff line
@@ -76,6 +76,18 @@ static inline int cpumask_to_vp_set(struct hv_flush_pcpu_ex *flush, 
{

	int cpu, vcpu, vcpu_bank, vcpu_offset, nr_bank = 1;



	/* valid_bank_mask can represent up to 64 banks */

	if (hv_max_vp_index / 64 >= 64)

		return 0;



	/*

	 * Clear all banks up to the maximum possible bank as hv_flush_pcpu_ex

	 * structs are not cleared between calls, we risk flushing unneeded

	 * vCPUs otherwise.

	 */

	for (vcpu_bank = 0; vcpu_bank <= hv_max_vp_index / 64; vcpu_bank++)

		flush->hv_vp_set.bank_contents[vcpu_bank] = 0;



	/*

	 * Some banks may end up being empty but this is acceptable.

	 */
@@ -83,11 +95,6 @@ static inline int cpumask_to_vp_set(struct hv_flush_pcpu_ex *flush, 
		vcpu = hv_cpu_number_to_vp_number(cpu);

		vcpu_bank = vcpu / 64;

		vcpu_offset = vcpu % 64;



		/* valid_bank_mask can represent up to 64 banks */

		if (vcpu_bank >= 64)

			return 0;



		__set_bit(vcpu_offset, (unsigned long *)

			  &flush->hv_vp_set.bank_contents[vcpu_bank]);

		if (vcpu_bank >= nr_bank)

arch/x86/include/asm/mshyperv.h

+1 −0
Original line number Diff line number Diff line
@@ -289,6 +289,7 @@ static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, u16 varhead_size, 
 * to this information.

 */

extern u32 *hv_vp_index;

extern u32 hv_max_vp_index;



/**

 * hv_cpu_number_to_vp_number() - Map CPU to VP.

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