linux-kernel - [RFC PATCH v3 03/12] x86/xen: Introduce new function to map HYPERVISOR_shared

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Date:   Fri, 14 Feb 2020 23:23:42 +0000
From:   Anchal Agarwal <anchalag@...zon.com>
To:     <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <hpa@...or.com>, <x86@...nel.org>, <boris.ostrovsky@...cle.com>,
        <jgross@...e.com>, <linux-pm@...r.kernel.org>,
        <linux-mm@...ck.org>, <kamatam@...zon.com>,
        <sstabellini@...nel.org>, <konrad.wilk@...cle.com>,
        <roger.pau@...rix.com>, <axboe@...nel.dk>, <davem@...emloft.net>,
        <rjw@...ysocki.net>, <len.brown@...el.com>, <pavel@....cz>,
        <peterz@...radead.org>, <eduval@...zon.com>, <sblbir@...zon.com>,
        <anchalag@...zon.com>, <xen-devel@...ts.xenproject.org>,
        <vkuznets@...hat.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <dwmw@...zon.co.uk>,
        <fllinden@...ozn.com>, <benh@...nel.crashing.org>
Subject: [RFC PATCH v3 03/12] x86/xen: Introduce new function to map
 HYPERVISOR_shared_info on Resume

Introduce a small function which re-uses shared page's PA allocated
during guest initialization time in reserve_shared_info() and not
allocate new page during resume flow.
It also  does the mapping of shared_info_page by calling
xen_hvm_init_shared_info() to use the function.

Signed-off-by: Anchal Agarwal <anchalag@...zon.com>
---
 arch/x86/xen/enlighten_hvm.c | 7 +++++++
 arch/x86/xen/xen-ops.h       | 1 +
 2 files changed, 8 insertions(+)

diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
index e138f7de52d2..75b1ec7a0fcd 100644
--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -27,6 +27,13 @@
 
 static unsigned long shared_info_pfn;
 
+void xen_hvm_map_shared_info(void)
+{
+	xen_hvm_init_shared_info();
+	if (shared_info_pfn)
+		HYPERVISOR_shared_info = __va(PFN_PHYS(shared_info_pfn));
+}
+
 void xen_hvm_init_shared_info(void)
 {
 	struct xen_add_to_physmap xatp;
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 45a441c33d6d..d84c357994bd 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -56,6 +56,7 @@ void xen_enable_syscall(void);
 void xen_vcpu_restore(void);
 
 void xen_callback_vector(void);
+void xen_hvm_map_shared_info(void);
 void xen_hvm_init_shared_info(void);
 void xen_unplug_emulated_devices(void);
 
-- 
2.24.1.AMZN