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| author | Paolo Bonzini <pbonzini@redhat.com> | 2019-07-31 09:15:32 +0200 |
|---|---|---|
| committer | Andrew Waterman <andrew@sifive.com> | 2019-08-16 14:14:12 -0700 |
| commit | 4bfae7862e436ce67c1aebaf2d95f0d35c658c51 (patch) | |
| tree | 90ac3a5d6468d635f05e4f862f7e5ab12639fa84 | |
| parent | 81300f89c4ac5f49b052b42ffe70924218d69a33 (diff) | |
| download | riscv-isa-manual-4bfae7862e436ce67c1aebaf2d95f0d35c658c51.zip riscv-isa-manual-4bfae7862e436ce67c1aebaf2d95f0d35c658c51.tar.gz riscv-isa-manual-4bfae7862e436ce67c1aebaf2d95f0d35c658c51.tar.bz2 | |
hypervisor: add performance counter delta registers
It has been requested that we add htimedelta[h] CSRs so that hosts can
lie to guests about the current time, without requiring trapping and
emulating. cycle is also included, since the SBI set timer callback has
absolute cycles as the argument. There is no intent to add equivalent
CSRs for instret and performance counters.
Fixes: #298
| -rw-r--r-- | src/hypervisor.tex | 47 | ||||
| -rw-r--r-- | src/priv-csrs.tex | 5 |
2 files changed, 52 insertions, 0 deletions
diff --git a/src/hypervisor.tex b/src/hypervisor.tex index 6ac03a1..47b90b2 100644 --- a/src/hypervisor.tex +++ b/src/hypervisor.tex @@ -404,6 +404,53 @@ indicating reads to the corresponding counter will cause an exception when V=1. Hence, they are effectively \warl\ fields. +\subsection{Hypervisor Time Delta Registers ({\tt htimedelta}, {\tt htimedeltah})} + +The {\tt htimedelta} CSR is a read/write register that contains the delta +between the value of the {\tt time} CSR and the value returned in VS-mode or +VU-mode. +That is, reading the {\tt time} CSR in VS or VU mode returns the sum of the +contents of {\tt htimedelta} and the actual value of {\tt time}. + +\begin{figure*}[h!] +{\footnotesize +\begin{center} +\begin{tabular}{@{}J} +\instbitrange{63}{0} \\ +\hline +\multicolumn{1}{|c|}{\tt htimedelta} \\ +\hline +64 \\ +\end{tabular} +\end{center} +} +\vspace{-0.1in} +\caption{Hypervisor time delta register, HSXLEN=64.} +\label{hdeltareg} +\end{figure*} + +For HSXLEN=32 only, {\tt htimedelta} holds the lower 32 bits of the +delta, and {\tt htimedeltah} holds the upper 32 bits of the delta. + +\begin{figure*}[h!] +{\footnotesize +\begin{center} +\begin{tabular}{@{}J} +\instbitrange{31}{0} \\ +\hline +\multicolumn{1}{|c|}{\tt htimedelta} \\ +\hline +\multicolumn{1}{|c|}{\tt htimedeltah} \\ +\hline +32 \\ +\end{tabular} +\end{center} +} +\vspace{-0.1in} +\caption{Hypervisor time delta registers, HSXLEN=32.} +\label{hdeltahreg} +\end{figure*} + \subsection{Hypervisor Guest Address Translation and Protection Register ({\tt hgatp})} \label{sec:hgatp} diff --git a/src/priv-csrs.tex b/src/priv-csrs.tex index fe78bab..166ff06 100644 --- a/src/priv-csrs.tex +++ b/src/priv-csrs.tex @@ -241,6 +241,11 @@ Number & Privilege & Name & Description \\ \hline \tt 0x680 & HRW &\tt hgatp & Hypervisor guest address translation and protection. \\ \hline +\multicolumn{4}{|c|}{Hypervisor Counter/Timer Virtualization Registers} \\ +\hline +\tt 0x605 & HRW &\tt htimedelta & Delta for VS/VU-mode timer. \\ +\tt 0x615 & HRW &\tt htimedeltah & Upper 32 bits of {\tt htimedelta}, RV32I only. \\ +\hline \multicolumn{4}{|c|}{Virtual Supervisor Registers} \\ \hline \tt 0x200 & HRW &\tt vsstatus & Virtual supervisor status register. \\ |